The compact disc (or CD) first appeared in the commercial marketplace in early 1982. Sony and Philips developed the CD as a joint venture and envisioned it as a reliable, high-quality replacement for aging phonograph technology. With the introduction of the audio CD, designers demonstrated that huge amounts of information can be stored simply and very inexpensively on common, non-magnetic media. Unlike previous recording media, the CD recorded data in digital form through the use of physical "pits" and "lands" in the disc. The digital approach allowed excellent stereo sound quality which does not degrade each time the disc is played, but also attracted the attention of PC designers who saw CDs as a natural solution for all types of computer information (i.e. text, graphics, programs, video clips, audio files, and so on). The CD-ROM drive is now standard equipment on both desktop and mobile PC systems.

While CD-ROM drives bring a great deal of reliable storage potential to the PC, it has not been possible to record CDs on the desktop - the technology required to create audio and computer CDs has traditionally been terribly complex and expensive, and limited by PC computing power of the day. Since the early 1990s, CD recorder (or CD-R) technology has steadily become more reliable and economical. Today, virtually any Pentium-based PC with a SCSI bus and 1GB or more of hard drive space can support a CD-R drive for under $500 (US). This chapter explains the technologies and troubleshooting techniques for CD-ROM and CD-R drives (Fig. 10-1).

CDs are mass-produced by stamping the pattern of pits and lands onto a molded polycarbonate disc (known as a substrate). It is this stamping process (much like the stamping used to produce vinyl records) that places the data on the disc. But the disc is not yet readable - there are finish steps that must be performed to transform a clear plastic disc into viable, data-carrying media. The clear polycarbonate disc is given a silvered (reflective) coating so that it will reflect laser light. Silvering coats all parts of the disc side (pits and lands) equally. After silvering, the disc is coated with a tough, scratch-resistant lacquer that seals the disc from the elements (especially oxygen which will oxidize and ruin the reflective coating). Finally, a label can be silk-screened onto the finished disc before it is tested and packaged. Figure 10-2 illustrates each of these layers in a cross-sectional diagram.

Recordable media appears very similar to the "pressed" CD media shown in Fig. 10-2 - but with two important variations. First, the polycarbonate CD-R substrate is pre-formed with a track spiral into which data will be written during recording. The substrate is then coated with a greenish translucent layer, and backed with a reflective layer of gold before protective laquer is applied over the gold. These translucent and gold layers allow the recorded pits and lands to be read back after recording.

CDs are not segregated into concentric tracks and sectors as magnetic media is. Instead, CDs are recorded as a single, continuous spiral track running from the spindle to the lead-out area. Figure 10-3 shows the spiral pattern recorded on a CD. The inset illustrates the relationship between the pits and lands. Each pit is about 0.12 m m (micrometers) deep and 0.6 m m wide. Pits and lands may range from 0.9 m m to 3.3 m m in length. There are approximately 1.6 m m between each iteration of the spiral. Given these microscopic dimensions, a CD-ROM disc offers about 16,000 tracks per inch (tpi).

During playback, CDs use a highly focused laser beam and laser detector to sense the presence or absence of pits. Figure 10-4 illustrates the reading behavior. The laser/detector pair is mounted on a carriage which follows the spiral track across the CD. A laser is directed at the underside of the CD where it penetrates more than 1 mm of clear plastic before shining on the reflective surface. When laser light strikes a land, the light is reflected toward the detector which, in turn, produces a very strong output signal. As laser light strikes a pit, the light is slightly out of focus. As a result, most of the incoming laser energy is scattered away in all directions, so very little output signal is generated by the detector. As with floppy and hard drives, it is the transition from pit to land (and back again) that corresponds to binary levels, NOT the presence or absence of a pit or land. The analog light signal returned by the detector must be converted to logic levels and decoded. A process known as eight-to-fourteen modulation (EFM) is very common with CD-ROMs.

A complex decoding process is necessary to convert the arcane sequence of pits and lands into meaningful binary information. The technique of eight-to-fourteen modulation (EFM) is used with CD-ROMs. For hard disk drives, techniques such as 2,7 RLL encoding can be used to place a large number of bits into a limited number of flux transitions. The same is true for CDs using EFM. User data, error correction information, address information, and synchronization patterns are all contained in a bit stream represented by pits and lands.

Magnetic media encodes bits as flux transitions - not the discrete orientation of any magnetic area. The same concept holds true with CD-ROMs where binary 1s and 0s do not correspond to pits or lands. A binary 1 is represented wherever a transition (pit-to-land or land-to-pit) occurs. The length of a pit or land represents the number of binary 0s. Figure 10-5 illustrates this concept. The eight-to-fourteen encoding technique equates each byte (eight bits) with a fourteen bit sequence (called a symbol) where each binary 1 must be separated by at least two binary 0s. Table 10-1 shows part of the eight-to-fourteen conversion. Three bits are added to merge each 14 bit symbol together.

A CD-ROM frame is composed of 24 synchronization bits, 14 control bits, 24 of the 14 bit data symbols you saw previously, and eight complete 14 bit error correction (EC) symbols. Keep in mind that each symbol is separated by an additional three merge bits, bringing the total number of bits in the frame to 588. Thus, 24 bytes of data is represented by 588 bits on a CD-ROM expressed as a number of pits and lands. There are 98 frames in a data block, so each block carries [98 x 24] 2,048 bytes (2,352 with error correction, synchronization, and address bytes). The basic CD-ROM can deliver 153.6KB of data (75 blocks) per second to its host controller.

Remember that the CD-ROM disc is recorded as one continuous spiral track running around the disk, so ordinary sector and track ID information that we associate with magnetic disks does not apply very well. Instead, information is divided in terms of 0 to 59 minutes, and 0 to 59 seconds recorded at the beginning of each block. A CD-ROM (like an audio CD) can hold up to 79 minutes of data. However, many CD-ROMs tend to limit this to 60 minutes since the last 14 minutes of data are encoded in the outer 5 mm of disk space which is the most difficult to manufacture and keep clean in everyday use. There are 270,000 blocks of data in 60 minutes. At 2,048 data bytes per block, the disk's capacity is 552,950,000 bytes (553MB). If all 79 minutes are used, 681,984,000 bytes (681MB) will be available in 333,000 blocks. Most CD-ROMs run between 553 and 650MB in normal production.

A compact disc is a remarkably reliable long-term storage media (conservative expectations place the life estimates of a current CD at about 100 years. However, the longevity of a CD is effected by its storage and handling - a faulty CD can cause file and data errors that you might otherwise interpret as a defect in the drive itself. Below are some tips to help protect and maintain the disc itself:

• Don't bend the disc. Polycarbonate is a forgiving material, but you risk cracking or snapping (and thus ruining) the disc.
• Don't heat the disk. Remember, the disc is plastic. Leaving it by a heater or on the dashboard of your car will cause melting.
• Don't scratch the disc. Laser wavelengths have a tendency to "look past" minor scratches, but a major scratch can cause problems. Be especially careful of circular scratches (one that follows the spiral track). A circular scratch can easily wipe out entire segments of data which would be unrecoverable.
• Don't use chemicals on the disc. Chemicals containing solvents such as ammonia, benzene, acetone, carbon tetrachloride, or chlorinated cleaning solvents can easily damage the disc’s plastic surface.

NOTE: Eventually, a buildup of excessive dust or fingerprints can interfere with the laser beam enough to cause disc errors. When this happens, the disc can be cleaned easily using a dry, soft, lint-free cloth. Hold the disc from its edges and wipe radially (from hub to edge). Do not wipe in a circular motion. For stubborn stains, moisten the cloth in a bit of fresh isopropyl alcohol (do not use water). Place the cleaned disc in a caddie or jewel case for transport and storage.

As a rule, recordable CDs are as rugged and reliable as ordinary "pressed" CDs. Still, you should exercise some rules in the careful handling and storage of recordable media:

• Maintain a comfortable environment. Don't expose recordable discs to sunlight or other strong light for long periods of time. Also avoid high heat and humidity which can damage the physical disc. Always keep blank or recorded media in clean "jewel" cases for best protection.
• Don’t write on the disc. Don't use alcohol-based pens to write on discs - the ink may eventually eat through the top (lacquer) surface and damage your data. Also don't use ball-point or other sharp-tipped pens because you may scratch right through the lacquer surface and damage the reflective gold layer (and ruin your data).
• Don’t use labels on the disc. Don't put labels on discs unless they are expressly designed for recordable CDs. The glue may eat through the lacquer surface just as some inks do, and/or the label may unbalance the disc and cause problems in reading it back or recording subsequent sessions. Never try to remove a label - you might tear off the lacquer and some of the reflecting surface.
• Watch your media quality. Many different brands of recordable CD media are now available in the marketplace. Quality varies from brand to brand (and even from batch to batch within a given brand). If you have repeated problems that can be traced to the blank media you are using, try using a different brand or even a different batch of the same brand.
• Don’t use Kodak Photo CDs. Avoid the use of Kodak Photo CDs on everyday CD recorders. Kodak Photo CDs are designed to be used only with Kodak Photo CD professional workstations. Although the discs are inexpensive, they have a protection bit which prevents them from being written on many CD recorders. When you attempt to write these discs on the recorders which recognize the protection bit, you will receive an error message.

Like so many other PC peripheral devices, the early CD-ROM faced a serious problem of industry standardization. Just recording the data to a CD is not enough - the data must be recorded in a way that any CD-ROM drive can read. Standards for CD-ROM data and formats were developed by consortiums of influential PC manufacturers and interested CD-ROM publishers. Ultimately, this kind of industry-wide cooperation has made the CD-ROM one of the most uniform and standardized peripherals in the PC market. With the broad introduction of CD recorders into the marketplace, it is also important for you to understand the major concepts and operations of CD recorders. This part of the chapter explains many of the key ideas needed to master CD-ROM and CD-R drives.

In 1984 (before the general release of CD-ROM), the PC industry realized that there must be a standard method of reading a disc's VTOC (Volume Table of Contents) - otherwise, the CD-ROM market would become extremely fragmented as various (incompatible) standards vied for acceptance. PC manufacturers, prospective CD publishers, and software developers met at the High Sierra Hotel in Lake Tahoe, CA to begin developing just such a uniform standard. By 1986, the CD-ROM standard file format (dubbed the High Sierra format) was accepted and approved. High Sierra remained the standard for several years, but has since been replaced by ISO 9660.

High Sierra was certainly a workable format, but it was primarily a domestic US development. When placed before the International Standards Organization (ISO), High Sierra was tweaked and refined to meet international needs. After international review, High Sierra was absorbed (with only few changes) into the ISO 9660 standard. Although many technicians refer to High Sierra and ISO 9660 interchangeably, you should understand that the two standards are NOT the same. For the purposes of this book, ISO 9660 is the current CD-ROM file format, and all CD recorders are capable of recording a disc in the ISO 9660 format.

By adhering to ISO 9660, CD-ROM drive makers can write software drivers (and use MSCDEX under MS-DOS) to enable a PC to read the CD's VTOC. ISO 9660 also allows a CD-ROM disc to be accessed by any computer system and CD-ROM drive that follows the standard. Of course, just because a disc is recognized does not mean that it can be used. For example, an ISO 9660-compliant Mac can access a ISO 9660 MPC disc, but the files on the disc can not be used by the Mac.

When Philips and Sony defined the proprietary standards that became CD audio and CD-ROM, the documents were bound in different colored covers. By tradition, each color now represents a different level of standardization. Red Book (a.k.a. Compact Disc Digital Audio Standard: CEI IEC 908) defines the media, recording and mastering process, and the player design for CD audio. When you listen to your favorite audio CD, you are enjoying the benefits of the Red Book standard. CDs conforming to Red Book standards will usually have the words "digital audio" printed below the disc logo. Today, Red Book audio may be combined with programs and other PC data on the same disc.

The Yellow Book standard (ISO 10149:1989) makes CD-ROM possible by defining the additional error correction data needed on the disc, and detection hardware and firmware needed in the drive. When a disc conforms to Yellow Book, it will usually be marked "data storage" beneath the disc logo. Mode 1 Yellow Book is the typical operating mode which supports computer data. Mode 2 Yellow Book (also known as the XA format) supports compressed audio data and video/picture data. The Yellow Book standards build on the Red Book, so virtually all CD-ROM drives are capable of playing back CD audio.

The Orange Book (a.k.a. Recordable Compact Disc Standard) is the key to CD recorders, and serves to extend the basic Red and Yellow Book standards by providing specifications for recordable products such as (Part 1) magneto-optical (MO) drives, and (Part 2) write-once CD-R drives. The Green Book standard defines an array of supplemental standards for data recording, and provides an outline for a specific computer system that supports CD-I (compact disc-interactive). Interactive kiosks and information systems using CD-I discs are based on Green Book standards. Blue Book is the standard for laser discs and their players. The White Book standards define CD-ROM video.

The Red Book standard defines CD audio as a stream of data that flows from the player mechanism to the amplifier (or other audio manipulation circuit) at a rate of 150KB/sec. This data rate was chosen to take music off the disc for truest reproduction. When the Yellow Book was developed to address CD-ROMs, this basic data rate was carried over. Designers soon learned that computer data can be transferred much faster than Red Book audio information, so the multi-spin (or multi-speed) drive was developed to work with Red Book audio at the normal 150KB/sec rate, but run faster for Yellow Book data in order to multiply the data throughput.

The first common multi-spin drives available were "2X" drives. By running at 2X the normal data transfer speed, data throughput can be doubled from 150KB/sec to 300KB/sec. If Red Book audio is encountered, the drive speed drops back to 150KB/sec. Increased data transfer rates make a real difference in CD-ROM performance - especially for data-intensive applications such as audio/video clips. CD-ROM drives with "4X" transfer speed (600KB/sec) can transfer data four times faster than a Red Book drive. Table 10-2 lists the average data rates for current CD-ROM drives.

One of the most fundamental problems writing software for PCs is the tremendous variability in the possible hardware and software configurations of individual machines. The selection of CPUs, motherboard chipsets, DOS versions, available memory, graphics resolutions, drive space, and other peripherals make the idea of a "standard" PC almost meaningless. Most software developers in the PC market use a base (or minimal) PC configuration to ensure that a product will run properly in a "minimal" machine. CD-ROM "multimedia" products have intensified these performance issues because of the unusually heavy demands posed by real-time audio and graphics. Microsoft assembled some of the largest PC manufacturers to create the Multimedia Personal Computer (or MPC) standard. By adhering to the MPC specification, software developers and consumers can anticipate the minimal capacity needed to run multimedia products.

NOTE: Appendix A outlines the three levels of MPC standards for the personal computer.

The limiting factor of a CD-ROM is its data transfer rate. Even a fast multi-spin CD-ROM takes a fairly substantial amount of time to load programs and files into memory - this causes system delays during CD-ROM access. If the PC could predict the data needed from a CD and load that data into RAM or virtual memory (i.e. the hard drive) during background operations, the effective performance of a CD-ROM drive can be enhanced dramatically. CD-ROM caching utilities provide a "look-ahead" ability that enables CD-ROMs continue transferring information in anticipation of use.

However, CD-ROM caching is a mixed blessing. The utilities required for caching must reside in conventional memory (or loaded into upper memory). In systems that are already strained by the CD-ROM drivers and other device drivers that have become so commonplace on PC platforms, adding a cache may prohibit some large DOS programs from running. Keep this in mind when evaluating CD-ROM caches for yourself or your customers.

NOTE: Windows 95 discontinues the use of SmartDrive in favor of its own internal caching features. If you are using Windows 95, you may optimize the CD-ROM cache through the File System Properties dialog. Click on Start, Settings, Control Panel, then double-click on the System icon. Select the Performance tab, and click the File System button, then select the CD-ROM tab. You can then optimize the CD-ROM cache size and access pattern.

Traditionally, CD-ROM drives have not been bootable devices. Since the CD-ROM drive needs software drivers, the PC always had to boot FIRST in order to load the drivers. This invariably required a bootable hard drive or floppy drive. When building a new system, this required you to boot from a floppy disk, install DOS and the CD-ROM drivers, and then pop in your Windows 95 CD for setup. In early 1995, the "El Torito" standard was finalized which provides the hardware and software specifications needed to implement a bootable CD-ROM. You need three elements to implement a bootable CD-ROM:

• a bootable CD-ROM drive mechanism (almost always fitted with an EIDE/IDE interface).
• a BIOS that supports the bootable CD-ROM (now common on many new motherboards).
• a CD with boot code and an operating system on it. If you don’t already have a bootable (or "system") CD, see "Creating a bootable CD" later in this chapter.

The Orange Book (Part II) is the primary specification for CD-R media, and all CD-R media should meet the Orange Book criteria for recordability and playback. Philips and Sony (the originators of the Orange Book specification) provide Orange Book certification of CD-R media. CD-R media which is NOT "Orange Book certified" should generally be avoided.

One of the problems with recording early CDs is that once the CD is written, it could not be appended. This means if 123MB of data is written to a CD, the remaining 527MB of storage potential on the disc is lost. CD developers sought a means of adding new data to a CD which has been previously recorded. This multisession capability means a CD to be written in terms of "sessions", and subsequent sessions can be linked to previous sessions - allowing the CD to be systematically filled.

A CD-R recorder that supports multisession recording can write a disc that will have multiple sessions linked together - each session containing its own lead-in, program and lead out areas. In effect, each session is treated as a different CD. Any multisession-capable CD-ROM can access the data in any session. By comparison, a "pressed" CD-ROM or a CD-R written in "Disc at Once" mode contains only one lead-in area, program area, and lead-out area.

NOTE: Some older CD-ROM drives which are NOT multisession-capable can only read the firat session of a multisession disc.

Each session written to a disc (whether multisession or single session) must be "fixed" before the session can be read. Fixation is the process of writing the session’s lead-in and lead-out information to the disc. This process finishes a writing session and creates a table of contents. Fixation is required before a CD-ROM or CD-Audio player can play the disc. Discs which are "fixated for append" can have additional sessions recorded later (each with their own session lead-in and lead-out) creating a multisession disc. When a disc is finalized, the absolute lead-in and lead-out for the entire disc is written, along with information which tells the reader not to look for subsequent sessions. This final table of contents (TOC) conforms to the ISO 9660 file standard.

Disc-at-Once is a CD writing mode that requires data to be written continuously without any interruptions, until the entire data set is transferred to the CD-R. The complete lead-in, program, and lead-out are written in a single writing process. All of the information to be recorded needs to be staged on the computer’s hard disk prior to recording in the Disc-at-Once mode. Recording in the Disc-at-Once mode eliminates the linking and run-in and run-out blocks associated with multisession and packet recording modes (which often are interpreted as uncorrectable errors during the glass mastering process).

NOTE: This mode is usually preferred for discs that are sent to a CD-ROM replication facility when CD-R is the source media.

The Track-at-Once writing mode is the key to multisession capability, and allows a session to be written in a number of discrete write events, called tracks because the written sessions contain complete "tracks" of information. The disc may be removed from the writer and read in another writer (given proper software) before the session is fixated.

Track-at-Once writing is a form of incremental write which mandates a minimum track length of 300 blocks and a maximum of 99 tracks per disc. A track written "at once" has 150 blocks of overhead for run-in, run-out, pre-gap and linking purposes. On the other hand, packet write is a method where several write events are allowed within a track, thus reducing the demands of overhead data. Each writing "packet" is bounded by 7 blocks of data: 4 for run-in, 2 for run-out, and 1 for linking.

Now that you have an understanding of CD-ROM/CD-R media and standards, it is time to review a drive in some detail. CD-ROM/CD-R drives are impressive pieces of engineering. The drive must be able to accept standard-sized disks from a variety of sources (each disk may contain an assortment of unknown surface imperfections). The drive must then spin the disk at a constant linear velocity (CLV) - that is, the disk speed varies inversely with the tracking radius. As tracking approaches the disk edge, disk speed slows, and vice versa. Keep in mind that CLV is different than the constant angular velocity (CAV) method used by floppy and hard drives which move the media at a constant speed. The purpose of CLV is to ensure that CD data is read at a constant rate. A drive must be able to follow the spiral data path on a spinning CD-ROM accurate to within less than 1 m m along the disk's radius. The drive electronics must be able to detect and correct any unforeseen data errors in real-time, operate reliably over a long working life, and be available for a low price that computer users have come to expect.

You can begin to appreciate how a CD drive achieves its features by reviewing the exploded diagram of Fig. 10-6. At the center of the drive is a cast aluminum or rigid stainless steel frame assembly. As with other drives, the frame is the single primary structure for mounting the drive's mechanical and electronic components. The front bezel, lid, volume control, and eject button attach to the frame, providing the drive with its clean cosmetic appearance, and offering a fixed reference slot for CD insertion and removal. Keep in mind that many drives use a sliding tray, so the front bezel (and the way it is attached) will not be the same for every drive.

The drive's electronics package has been split into several PC board assemblies: the main PCB which handles drive control and interfacing, and the headphone PCB which simply provides an audio amplifier and jack for headphones. The bulk of the drive's actual physical work, however, is performed by a main CD subassembly called a drive engine, which are often manufactured by only a few companies. As a result, many of the diverse CD-ROM drives on the market actually use identical "engines" to hold/eject, spin, and read the disk. This interchangeability is part of the genius of CD-ROM drives - a single sub-assembly performs 80% of the work. Sony, Philips, and Toshiba are the major manufacturers of CD-ROM engines, but other companies such as IBM and Ikka are also producing engines.

A typical drive engine is shown in Fig. 10-7. The upper view of the engine features a series of mechanisms that accept, clamp, and eject the disk. The foundation of this engine is the BC-7C assembly. It acts as a sub-frame which everything else is mounted to. Notice that the sub-frame is shock-mounted with four rubber feet to cushion the engine from minor bumps and ordinary handling. Even with such mounting, a CD-ROM drive is a delicate and fragile mechanism. The slider assembly, loading chassis assembly, and the cover shield provide the mechanical action needed to accept the disk and clamp it into place over the drive spindle, as well as free the disk and eject it on demand. A number of levers and oil dampers serve to provide a slow, smooth mechanical action when motion takes place. A motor/gear assembly drives the load/unload mechanics.

The serious work of spinning and reading a disk is handled under the engine as shown in Fig. 10-8. A spindle motor is mounted on the sub-frame and connected to a spindle motor PC board. A thrust retainer helps keep the spindle motor turning smoothly. The most critical part of the CD engine is the optical device containing the 780nm (nanometer) 0.6mW gallium aluminum arsenide (GaAlAs) laser diode and detector, along with the optical focus and tracking components. The optical device slides along two guide rails and shines through an exposed hole in the sub-frame. This combination of device mounting and guide rails is called a sled.

A sled must be made to follow the spiral data track along the disk. While floppy disks (using clearly defined concentric tracks) can easily make use of a stepping motor to position the head assembly, a CD drive ideally requires a linear motor to act much like the voice coil motor used to position hard drive R/W heads. By altering the signal driving a sled motor and constantly measuring and adjusting the sled's position, a sled can be made to track very smoothly along a disk - free from the sudden, jerky motion of stepping motors. Some CD drives still use stepping motors with an extremely fine-pitch lead screw to position the sled. The drive's main PC board is responsible for managing these operations.

The electronics package used in a typical CD-ROM drive is illustrated in Fig. 10-9. The electronics package can be divided into two major areas; the controller section and the drive section. The controller section is dedicated to the peripheral interface - its connection to the adapter board. Much of the reason for a CD-ROM's electronic sophistication can be traced to the controller section. Notice that the controller circuitry shown in Fig. 10-9 is dedicated to handling a SCSI interface. This allows the unit's "intelligence" to be located right in the drive itself. You need only connect the drive to a system-level interface board (a SCSI adapter) and set the drive's device number to establish a working system. Most current, low-cost CD-ROM drives will use an EIDE/IDE interface (the same interface used for hard drives).

The drive section manages the CD-ROM's physical operations (i.e. load/unload, spin the disk, move the sled, and so on), as well as data decoding (EFM) and error correction. Drive circuitry converts an analog output from the laser diode into an EFM signal which is, in turn, decoded into binary data and CIRC (Cross-Interleaved Reed-Solomon Code) information. A drive controller IC and servo processor IC are responsible for directing laser focus, tracking, sled motor control (and feedback), spindle motor control (and feedback), and loading/unloading motor control.

When it comes to CD drive electronics, you should treat the diagram of Fig. 10-9 more as a guideline than as an absolute. There are quite a few different iterations of drive electronics and interfaces; while many manufacturers use SCSI interfaces, most systems the EIDE/IDE system-level interface, and several manufacturers implement proprietary interfaces (in some cases, these are often subtle, non-standard variations of SCSI or IDE interfaces). Obtain manufacturer's service data wherever possible for specific information on your particular drive.

Hardware alone is not enough to implement a CD-ROM or CD-R drive. In an ideal world, BIOS and MS-DOS would provide the software support to handle the drive, but in practice, the variations between CD-ROM designs and interfaces make it impractical to provide low-level BIOS services. Manufacturers provide a hardware-specific device driver used to communicate with the CD-ROM and interface. An MS-DOS extension (MSCDEX) provides file handling and logical drive letter support. This part of the chapter explains the operations and features of CD-ROM device drivers and MSCDEX.

A low-level device driver allows programs to access the CD-ROM or CD-R drive properly at the register (hardware) level. Since most CD-ROM/CD-R drives are designed differently, they require different device drivers. If you change or upgrade the drive at any point, the device driver must be upgraded as well. A typical device driver uses a .SYS extension, and is initiated by adding its command line to the PC's CONFIG.SYS file such as;

DEVICE=HITACHIA.SYS /D:MSCD000 /N:1 /P:300

NOTE: the DEVICE command may be replaced by the DEVICEHIGH command if you have available space in the upper memory area (UMA).

A CD-ROM/CD-R device driver will typically have three command line switches associated with it. These parameters are needed to ensure that the driver installs properly. For the example command line shown above, the /D switch is the name used by the driver when it is installed in the system's device table. This name must be unique, and matched by the /D switch in the MSCDEX.EXE command line (covered later). The /N switch is the number of CD-ROM drives attached to the interface card. The default is 1 (which is typical for most general-purpose systems). Finally, the /P switch is the I/O port address the drive’s adapter card resides at. As you might expect, the port address should match the port address on the physical interface. If there is no /P switch, the default is 0300h.

There’s an additional wrinkle when using CD recorders - virtually all internal CD-R drives use the SCSI interface. This means the PC must be fitted with a SCSI adapter, and configured with an ASPI driver in order to allow the SCSI adapter to interface to the drive (this is also true if you’re using a SCSI CD-ROM drive). A typical ASPI driver entry would appear in CONFIG.SYS such as:

DEVICE=C:\SCSI\ASPIPPA3.SYS /L=001

NOTE: If there are no SCSI hard drives in the system, the SCSI adapter’s on-board BIOS ROM can usually be disabled.

MS-DOS was developed in a time when no one anticipated that large files would be accessible to a PC, and it is severely limited in the file sizes that it can handle. With the development of CD-ROMs, Microsoft created an extension to MS-DOS that allows software publishers to access 650MB CDs in a standard fashion - the Microsoft CD-ROM Extensions (MSCDEX). As with most software, MSCDEX offers some vital features (and a few limitations), but it is required by a vast majority of CD-ROM/CD-R products. Obtaining MSCDEX is not a problem - it is generally provided on the same disk containing the CD-ROM's low-level device driver. New versions of MSCDEX can be obtained from the Microsoft web site (www.microsoft.com), or from the Microsoft forum on CompuServe (GO MSL-1).

In actual operation, MSCDEX is loaded in the AUTOEXEC.BAT file. It should be loaded after any mouse driver, and loaded before any MENU, SHELL, DOSSHELL, or WIN line. It should also be loaded before any .BAT file is started. Keep in mind that if a .BAT file loads a network, MSCDEX must be included in the batch file after the network driver. Further, MSCDEX must be loaded after that network driver with the /S (share) switch in order to hook into the network driver chain. If you want to use the MS-DOS drive caching software (SmartDrive) to buffer the CD-ROM drive(s), load MSCDEX before SmartDrive. The MSCDEX /M (number of buffers) switch can be set to 0 when using SmartDrive. If you find that SmartDrive is interfering with MPC applications like Video for Windows, you can load SmartDrive before MSCDEX., and set the /M switch for at least 2. When loading MSCDEX, remember that the MSCDEX /D switch MUST match the /D label used in the low-level driver. Otherwise, MSCDEX will not load. If SETVER is loaded in the CONFIG.SYS file, be sure to use the latest version of MSCDEX.

Although the vast majority of CD-ROM bundles include installation routines that automate the installation process for the low-level driver and MSCDEX, you should understand the various command line switches (shown in Table 10-3) that make MSCDEX operate. Understanding these switches may help you to overcome setup problems.

With the acceptance of the "El Torito" standard for IDE CD-ROM drives, it is now possible to boot your PC from a CD and load an operating system without a floppy or hard drive. The problem is in obtaining bootable CDs to begin with. Many new computers are being sold with a "system disc" which can boot and load an operating system, but it is rare for users to bring in their bootable CDs with the system when service is required. If you have a CD-R drive and some readily available software tools, you can actually make a bootable CD yourself. This part of the chapter discusses the procedure used to create a bootable CD. Before you can create a bootable CD, you will need a system (or access to a system) with the following hardware and software tools:

• An "El Torito-capable" IDE or SCSI CD-ROM drive (with their standard IDE/SCSI interfaces).
• An "El Torito-capable" motherboard or SCSI adapter BIOS that supports booting from bootable CDs.
• A hexadecimal editor utility. If you have Norton Utilities (version 8.0 or Windows 95), the DISKEDIT.EXE utility is preferred.
• A bootable floppy disk (MS-DOS 6.2x or DOS 7.0 of Windows 95). You may also use a bootable hard drive.
• A hard disk drive with ample speed and space to hold an ISO 9660 image file for the bootable CD. A SCSI disk is preferred, but a fast EIDE hard drive will also work. There should be at least 650MB of free space on the HDD for the image file.
• A CD-R drive (almost always SCSI).
• Any CD-R software that can make an ISO 9660 image file. For example, you could use Adaptec's Easy CD Pro for Windows 95.
• A blank CD-R disc (you can’t make a multisession CD bootable).

NOTE: Creating a bootable CD is a rather lengthy and sophisticated procedure which requires some knowledge of editing hexadecimal files and creating ISO image files. You may choose to seek the advice and guidance of more experienced personnel before proceeding on your own.

Companion CD: If you need a hex editor, try HW16V210.ZIP on the Companion CD.

In order to boot from a CD, there must be a "Boot Volume Descriptor" (or BVD) located at sector 17 of the CD. The BVD is a string of hex codes. Somewhere in those hex codes, there must be a series of 4 bytes that list the starting address of the "Booting Catalog" (or BC). The BC is another set of hex codes which describe several different aspects of the CD. Again, there must have a sequence of 4 bytes that indicates the starting address of a bootable image file.

The actual process of making a bootable CD consists of roughly 5 steps. First, we’ll make an image file of the bootable floppy (or hard) disk with the hex editor (i.e. DISKEDIT.EXE). We’ll name the file OSBOOT.IMG. Next, we’ll make a booting catalog file which we’ll name BOOTCAT.BIN. Third, we’ll make an ISO 9660 image file that contains the above 2 files - as well as other files and directories to be written to the CD. We’ll edit the ISO file using the hex editor. Finally, we’ll burn that ISO 9660 image file to the blank CD-R disc.

Before making a bootable image file of your floppy (or hard) disk, pay particular attention to your CD-ROM drivers. If you create a bootable CD without the CD-ROM drivers and MSCDEX, you’ll simply create an "image" if the A: (or C:) drive. This will allow you to boot from the CD, but the other files and directories on the CD will not be accessible because the CD-ROM drivers will not be loaded. You MUST include the CD-ROM drivers if you wish the other (non-booting) files on the CD to be available after the boot process has finished. In fact, some more experienced technicians have developed a multi-boot menu in CONFIG.SYS which allows them to select low-level CD-ROM drivers for MANY possible drives (this allows the same bootable CD to be accessible on many different drives). If you’re using Norton’s DISKEDIT.EXE, follow the steps below to create an image file:

1. Select Object, Drive, then A: (or B: or C: depending on what bootable disk you care to take an image from) .

2. Select Object, Physical Sector, and OK.

3. Select Tools, Write Object to, then choose To a File.
1. Enter the file name (i.e. OSBOOT.IMG), then select Yes to save the file.

NOTE: Remember that the actual file used to boot the CD is just an image of another bootable drive. The other files "outside" the bootable image file (after the CD has booted) can only be found after the CD-ROM drivers have been loaded by an appropriate CONFIG.SYS and AUTOEXEC.BAT file.

The next step is to create a booting catalog file. There is no tool to do this automatically, so you’ll have to handle this manually. Create a hex file (we’ll call it BOOTCAT.BIN) using your hex editor. The file should be 2048 bytes long. Use DISKEDIT (or your own hex editor) to edit the BOOTCAT.BIN file like this:

The rest of this file must be filled with hex 00. The last "BB" in the file has no meaning, and will be changed later - we’re just using it to mark the place where the OSBOOT.IMB file address should go.

Now we must create an ISO 9660-compatible file which contains our booting catalog, the bootable image file, and any other files and directories we want to be on the bootable CD. You can use virtually any CD-R authoring software you wish (i.e. Easy CD Pro for Windows 95). Most CD-R authoring software now uses a "drag-and-drop" interface for defining the files which will be placed on the CD. The order in which files are "dragged and dropped" into the workspace is the order in which they will be written. Make the booting catalog (BOOTCAT.BIN) your first file on the CD-R, then make the bootable image file (OSBOOT.IMG) your second file on the CD-R. After that, you can simply "drag-and-drop" any other files and directories which will be written on the CD.

NOTE: Some technicians have reported that placing the booting catalog and bootable image file at the END of the CD-R will still work with SCSI CD-ROM drives, but not with IDE CD-ROM drives, but placing the files at the beginning of the CD-R should work in all cases.

Once you have all the desired files defined for the new bootable CD, go ahead and generate the ISO 9660 image file to your hard drive (keep in mind that there must be sufficient space on the hard drive to hold the entire image file - up to 650MB).

This is perhaps the trickiest part of the process because you will use your hex editor to modify the ISO 9660 image file before burning the file to a blank CD-R disc. Start DISKEDIT.EXE (or whatever other hex editor you’re using), then load the image file you just created. Depending on the amount of material you added to the image file, it can be quite lengthy.

1. Find the ASCII string in "BOOTCAT". Put your active cursor at the "B", then move the cursor up 2 lines and right 1 space. Write down the next 4 bytes. For example, if you move the cursor and the next four bytes read 15 00 00 00, then write down "15 00 00 00" on a sheet of paper for later use.
1. Find the ASCII string in "OSBOOT". Put your active cursor at the "O", then move the cursor up 2 lines and right 1 space. Write down the next 4 bytes. For example, if you move the cursor and the next four bytes read 16 00 00 00, then write down "16 00 00 00" on a sheet of paper for later use.
1. Find the Hex string "AA 55 55 AA". It is located in the sector occupied by the BOOTCAT.BIN file. You will find a "BB" (where you placed it) in the 3rd row of this sector. From this place, fill in the 4 bytes obtained from finding the "OSBOOT" ASCII string (i.e. 16 00 00 00). For example, the line which said:

NOTE: That "02" in the 2nd byte of this row means it's a 1.44MB floppy bootable image. If you use other media for the bootable image, change it to: 01 for a 1.2MB floppy disk, 02 for a 1.44MB floppy disk, 03 for a 2.88MB floppy disk, or 04 for a hard disk.

4. Edit sector 17 of the ISO file. Go back to the beginning (sector 0) of this ISO image file, then press PageDown key to offset 34816 (decimal) - this is the beginning of sector 17. Replace the hex codes from the beginning of this sector with the following:

At this point, use your CD-R authoring tool to "burn" the modified ISO 9660 image file to the CD-R disc. The writing process may take several minutes to as much as an hour depending on the amount of programs and data being transferred to the disc. If you want extra safety, have the authoring software test the writing process for proper data transfer before starting to write.

For an IDE CDROM, you just have to change the setting of booting sequence in BIOS to "CDROM, C:, A:", then reboot the PC with the bootable CD in CD-ROM drive. For SCSI CD-ROM drives, the booting sequence of the motherboard BIOS should be changed to "SCSI, IDE". If the BIOS doesn’t have this option, you’ll just have to temporarily set all the IDE HDD entries to "none" or "not installed". Next, enter the BIOS setting of your SCSI card. For example, in Adaptec's AHA 2940U, go into "Advanced Configuration Options", enable the options; "Host Adapter BIOS (Configuration Utility Reserve BIOS Space)" and "BIOS Support for Bootable CD-ROM". Then reboot the PC with the bootable CD in the drive.

Companion CD: If you like the idea of creating your own bootable CDs, but don’t like the idea of editing hex code manually, try the following utilities on the Companion CD: mkbtcd1.zip, bootiso.zip, and bcd.zip.

Though the vast majority of CD-ROM problems are due to software or setup problems, the drives themselves are delicate and unforgiving devices. Considering that their prices have plummeted over the last few months (and still continue to drop), there is little economic sense in attempting a lengthy repair. When a fault occurs in the drive or in its adapter board, your best course is typically to replace the defective drive outright.

Companion CD: The companion CD contains a number of CD-ROM testing/caching utilities. Check out CDCP10.ZIP, CDQCK120.ZIP, and CDSPEED.ZIP.

Symptom 10-1. The drive has trouble accepting or rejecting a CD. This problem is typical of motorized CD-ROM drives where the disc is accepted into a slot, or placed in a motorized tray. Before performing any disassembly, check the assembly through the CD slot for any obvious obstructions. If there is nothing obvious, expose the assembly and check each linkage and motor drive gear very carefully. Carefully remove or free any obstruction. Be gentle when working around the load/unload assembly. Notice how it is shock mounted in four places.

Disconnect the geared DC motor assembly and try moving the load/unload mechanism by hand. If you feel any resistance or obstruction, you should track it down by eye and by feel. Replace any worn or damaged part of the mechanism, or replace the entire load/unload assembly. Also check the geared motor for any damage or obstruction. Broken or slipping gear teeth can interfere with the transfer of force from motor to mechanism. Replace any damaged gears or replace the entire geared assembly. You may also simply replace the CD-ROM drive mechanism outright.

Symptom 10-2. Optical read head does not seek. An optical head is used to identify pits and lands along a CD-ROM, and to track the spiral data pattern as the head moves across the disk. The optical head must move very slowly and smoothly to ensure accurate tracking. Head movement is accomplished using a linear stepping motor (or linear actuator) to shift the optical assembly in microscopic increments - head travel appears perfectly smooth to the unaided eye. Check the drive for any damaged parts of obstructions. When the optical head fails to seek, the easiest and fastest fix is simply to replace the CD-ROM mechanism outright.

Symptom 10-3. Disc cannot be read. This type of problem may result in a DOS level "sector not found" or "drive not ready" error. Before you reach for your tools, however, check the CD itself to ensure that it is the right format, inserted properly, and physically clean. Cleanliness is very important to a CD. While the laser will often "look past" any surface defects in a disc, the presence of dust or debris on a disc surface can produce serious tracking (and read) errors. Try a different disc to confirm the problem. If a new or different disc reads properly, the trouble may indeed be in (or on) the original disc itself. Not only the disc must be clean, but the head optics must also be clear. Gently dust or clean the head optics as suggested by your drive's particular manufacturer.

If read problems persist, check the physical interface cable between the drive and its adapter board. Be sure that the cable is connected correctly and completely. Many CD drives use SCSI interfaces - if you are using multiple SCSI devices from the same controller card and other SCSI devices are operating properly, the SCSI controller board is probably intact. If other SCSI devices are also malfunctioning, try a new SCSI host controller board. At this point, either the drive's optical head or electronics are defective. Your best course here is to try replacing the drive. If problems persist on a drive with a proprietary interface, replace the adapter board.

Symptom 10-4. The disc does not turn. The disc must turn at a constant linear velocity (CLV) which is directed and regulated by the spindle. If the disc is not spinning during access, check to be sure that the disc is seated properly, and is not jammed or obstructed. Before beginning a repair, review your drive installation and setup carefully to ensure that the drive is properly configured for operation. If the drive's BUSY LED comes on when drive access is attempted (you may also see a corresponding DOS error message), the drive spindle system is probably defective. If the computer does not recognize the CD drive (i.e. "invalid drive specification"), there may be a setup or configuration problem (either the low-level device driver or MSCDEX may not have loaded properly). If your particular drive provides you with instructions for cleaning the optical head aperture, perform that cleaning operation and try the drive again. A fouled optical head can sometimes upset spindle operation. If operation does not improve, replace the CD-ROM drive mechanism.

Symptom 10-5. The optical head can not focus its laser beam. As you saw earlier in this chapter, a CD-ROM drive must focus its laser beam to microscopic precision in order to properly read the pits and lands of a disk. To compensate for the minute fluctuations in disc flatness, the optical head mounts its objective lens into a small focusing mechanism which is little more than a miniature voice coil actuator - the lens does not have to move very much at all to maintain precise focus. If focus is out or not well maintained, the laser detector may produce erroneous signals. This may result in DOS drive error messages.

If random but consistent DOS errors appear, check the disc to be sure that it is optically clean - dust and fingerprints can result in serious access problems. Try another disc. If a new disc continues to perform badly, try cleaning the optical aperture with clean (photography-grade) air. When problems persist, the optical system is probably damaged or defective. Try replacing the CD-ROM drive mechanism outright.

Symptom 10-6. There is no audio being generated by the drive. Many CD-ROM drives are capable of not only reading computer data, but reading and reproducing music and sounds under computer control. Audio CDs can often be played in available CD-ROM drives through headphones or speakers. Start your investigation by testing the headphones or speakers in another sound source such as a stereo. Once you have confirmed that the speakers or headphones are working reliably, check the drive's audio volume setting which is usually available through the front bezel. Set the volume to a good average place (perhaps mid-range). Make sure that the disk you are trying to play actually contains valid Red Book audio. Check any software required to operate the CD drive's audio output (usually set with a "mixer applet") to be sure that it is installed and loaded as expected. CD-ROMs will not play audio CDs without an audio driver. Also check the line output which would drive amplified speakers or stereo inputs. If speakers work through the line output but headphones or speakers do not work through the front bezel connector, the volume control or output audio amplifier may be defective. If the headphone output continues to fail, replace the headphone PC board or replace the entire CD-ROM drive outright.

Symptom 10-7. Audio is not being played by the sound card. Normally, the sound card will not play Red Book audio from a CD - that is usually fed directly to the CD's headphone or line output. However, audio can be channeled to the sound board for playback. Most CDs offer an audio connector that allows audio signals to be fed directly to the sound board. If this "CD audio cable" is missing or defective, Red Book audio will not play through the sound board. Check or replace the cable. If the cable is intact (and audio IS available from the CD-ROM headphone output), check the sound board’s configuration for any "mixer" applet (see that any control for CD audio is turned up, and remember to save any changes). If problems persist, try replacing the sound board. If the CD audio cable is intact (and audio is NOT available from the CD-ROM headphone output), the audio amplifier circuit in the CD-ROM is probably defective - try replacing the CD-ROM drive.

Symptom 10-8. You see a "Wrong DOS version" error message when attempting to load MSCDEX. You are running MS-DOS 4, 5, or 6 with a version of MSCDEX which does not support it. The solution is then to change to the correct version of MSCDEX. The version compatibility for MSCDEX is shown below:

• v1.01 14,913 bytes (No ISO9660 support - High Sierra support only)
• v2.00 18,307 bytes (High Sierra and ISO9660 support for DOS 3.1-3.3)
• v2.10 19,943 bytes (DOS 3.1-3.3 and 4.0 - DOS 5.x support provided with SETVER)
• v2.20 25,413 bytes (same as above with Win 3.x support - changes in audio support)
• v2.21 25,431 bytes (DOS 3.1-5.0 support with enhanced control under Win 3.1)
• v2.22 25,377 bytes (DOS 3.1-6.0 & higher with Win 3.1 support)
• v2.23 25,361 bytes (DOS 3.1-6.2 and Win 3.1 support - supplied with MSDOS 6.2)

When using MS-DOS 5.x to 6.1, you will need to add the SETVER utility to CONFIG.SYS in order to use MSCDEX v2.10 or v2.20 properly (i.e. DEVICE = C:\DOS\SETVER.EXE). SETVER is used to tell programs that they are running under a different version of DOS than DOS 5.0. This is important since MSCDEX (v2.10 and v2.20) refuses to work with DOS versions higher than 4.0. SETVER is used to fool MSCDEX into working with higher versions of DOS. In some versions of DOS 5.0 (such as Compaq DOS 5.0), you will need to add an entry to SETVER for MSCDEX (i.e. SETVER MSCDEX.EXE 4.00). This entry modifies SETVER without changing the file size or date.

Symptom 10-9. You can not access the CD-ROM drive letter. You may see an error message such as "Invalid drive specification". This is typically a problem with the CD-ROM drivers. The MS-DOS extension MSCDEX has probably not loaded. Switch to the DOS sub-directory and use the MEM /C function to check the loaded drivers and TSRs. If you see the low-level driver and MSCDEX displayed in the driver list, check the CD-ROM hardware. Make sure that the data cable between the drive and adapter board in inserted properly and completely. If problems persist, try replacing the adapter board. If you do NOT see the low-level driver and MSCDEX shown in the driver list, inspect your CONFIG.SYS and AUTOEXEC.BAT files. Check that the drivers are included in the startup files to begin with. Make sure that the label used in the /D switch is the same for both the low-level driver and MSCDEX. If the label is not the same, MSCDEX will not load. If you are using MS-DOS 5.0, be sure the SETVER utility is loaded. You could also try updating MSCEDX to v2.30.

Symptom 10-10. You see an error when trying to load the low-level CD-ROM driver. Check that you are using the proper low-level device driver for your CD-ROM drive. If you are swapping the drive or adapter board, you probably need to load a new driver. If the driver fails to load with original hardware, the adapter board may have failed, or its jumper settings may not match those in the driver’s command line switches. Check the signal cable running between the drive and adapter board. If the cable is crimped or scuffed, try replacing the cable. Next, try replacing the adapter board. If problems persist, try replacing the CD-ROM drive mechanism itself.

Symptom 10-11. You see an error such as "Error: not ready reading from drive D:". Check that a suitable disc is inserted in the drive and that the drive is closed properly. Make sure that the low-level device driver and MSCDEX are loaded correctly. If the drivers do not load, there may be a problem with the adapter board or drive mechanism itself. Also check that the data cable between the drive and adapter is connected properly and completely. If problems persist, suspect a weakness in the PC power supply (especially if the system is heavily loaded or upgraded). Try a larger supply in the system. If problems persist, replace the CD-ROM drive. If a new drive does not correct the problem, try a different interface adapter.

Symptom 10-12. SmartDrive is not caching the CD-ROM properly. The version of SmartDrive supplied with DOS 6.2x provides three forms of caching, although older forms of SmartDrive (such as the ones distributed with Windows 3.1, DOS 6.0 and 6.1) will not adequately cache CD-ROM drives. The BUFFERS statement also does not help caching. So if you are looking to SmartDrive for CD-ROM cache, you should be using the version distributed with DOS 6.2x. You should also set BUFFERS=10,0 in the CONFIG.SYS file, and the SmartDrive command line should come after MSCDEX. When using SmartDrive, you can change the buffers setting in the MSCDEX command line (/M) to 0 - this allows you to save 2KB per buffer.

NOTE: SmartDrive is NOT used by Windows 95 which employs its own CD caching scheme. Try disabling SmartDrive when running under Windows 95.

Symptom 10-13. The CD-ROM drivers will not install properly on a drive using compression software. This is usually because you booted from a floppy disk and attempted to install drivers without loading the compression software first. Before doing anything else, check the loading order - allow your system to boot from the hard drive before installing the CD-ROM drivers. This allows the compression software to assign all drive letters. As an alternative, boot from a compression-aware floppy disk. If you must boot the system from a floppy disk, make sure the diskette is configured to be fully compatible with the compression software being used.

Symptom 10-14. You see an error indicating that the CD-ROM drive is not found. This type of problem may also appear as loading problems with the low-level driver. There are several possible reasons why the drive hardware cannot be found. Check the power connector first, and make sure the 4-pin power connector is inserted properly and completely. If the drive is being powered by a "Y-connector", make sure any interim connections are secure. Use a voltmeter and measure the +5 volt (pin 4) and +12 volt (pin 1) levels. If either voltage (especially the +12 volt supply) is unusually low or absent, replace the power supply. Check the signal connector next and see that the drive’s signal interface cable is connected securely at both the drive and controller. If the cable is visibly worn or damaged, try a new one.

Inspect the drive interface adapter and make sure that the adapter’s IRQ, DMA, and I/O address settings are correct. They must also match with the command line switches used with the low-level driver. If the adapter is for a CD-ROM alone, you may also try installing the adapter in a different bus slot. If your CD-ROM uses a SCSI interface, make sure that the SCSI bus is properly terminated at both ends. If problems persist, replace the drive adapter.

Symptom 10-15. After installing the CD-ROM drivers, system reports significantly less available RAM. This is usually a caching issue with CD-ROM driver software, and you may need to adjust the CD-ROM driver software accordingly. This type of problem has been documented with Teac CD-ROM drives and CORELCDX.COM software. If the software offers a command line switch to change the amount of XMS allocated, reduce the number to 512 or 256. Check with tech support for your particular drive for the exact command line switch settings.

Symptom 10-16. In a new installation, the driver fails to load successfully for the proprietary interface card. In almost all cases, the interface card has been configured improperly. Check the drive adapter card first. Make sure that the drive adapter is configured with the correct IRQ, DMA, and I/O address settings, and check for hardware conflicts with other devices in the system. In some cases, you may simply enter the drive maker (i.e. Teac) as the interface type during driver installation. Make sure that the interface is set properly for the system, and your particular drive. Check the driver’s command line next - the driver’s command line switches should correctly reflect the drive adapter’s configuration.

Symptom 10-17. The CD-ROM driver loads, but you see an error such as; "CDR101" (drive not ready), or; "CDR103" (CDROM disk not HIGH SIERRA or ISO). You are using a very old version of the low-level driver or MSCDEX. Check your driver version (it may be outdated). Contact the drive manufacturer’s tech support and see that you have the very latest version of the low-level driver. For very old drives, there may also be a later "generic" driver available. Check your version of MSCDEX next. Since low-level drivers are often bundled with MSCDEX, you may also be stuck with an old version of MSCDEX. You can usually download a current version of MSCDEX from the same place you get an updated low-level driver, or download it from Microsoft at; www.microsoft.com.

Symptom 10-18. You are having trouble setting up more than one CD-ROM drive. You must be concerned about hardware and software issues. Check the drive adapter first - make sure that the drive adapter will support more than one CD-ROM on the same channel. If not, you will have to install another drive adapter to support the new CD-ROM drive. Low-level drivers present another problem since you will need to have one copy of a low-level driver loaded in CONFIG.SYS - one for each drive. Make sure that the command line switches for each driver match the hardware settings of the corresponding drive adapter. Finally, check your copy of MSCDEX. You need only one copy of MSCDEX in AUTOEXEC.BAT, but the "/D:" switch must appear twice - once for each drive ID.

Symptom 10-19. Your CD-ROM drive refuses to work with an IDE port. It may very well be that the drive uses a non-standard port (other than IDE). Try replacing the drive adapter board. You must connect the CD-ROM drive to a compatible drive adapter. If the drive is proprietary, it will not interface to a regular IDE port. It may be necessary to purchase a drive adapter specifically for the CD-ROM drive.

Symptom 10-20. You cannot get the CD-ROM drive to run properly when mounted vertically. CD-ROM drives with "open" drive trays cannot be mounted vertically - disc tracking simply will not work correctly. The only CD-ROM drives that can be mounted vertically are those with caddies, but you should check with those manufacturers before proceeding with vertical mounting.

Symptom 10-21. The SCSI CD-ROM drive refuses to work when connected to an Adaptec SCSI interface. Other drives are working fine. This is a common type of problem among SCSI adapters, and is particularly recognized with Adaptec boards because of their great popularity. In most cases, the Adaptec drivers are the wrong version, or are corrupted. Try turning off Sync Negotiations on the Adaptec SCSI interface, and reboot the system. Your SCSI drivers may also be buggy or outdated. Check with Adaptec technical support (www.adaptec.com) to determine if there are later drivers that you should use instead.

Symptom 10-22. You see a "No drives found" error when the CD-ROM driver line is executed in CONFIG.SYS. In most cases, the driver command line switches do not match the hardware configuration of the drive adapter. Your low-level driver may be missing or incomplete. Open CONFIG.SYS into a word processor and see that the low-level driver has a complete and accurate command line. See that any command line switches are set correctly. Check the MSCDEX command line next. Open AUTOEXEC.BAT into a word processor and see that the MSCDEX command line is accurate and complete. Also confirm that any MSCDEX command line switches are set correctly. If you are using SmartDrive with DOS 6.0 or later, try adding the /U switch to the end of your SmartDrive command line in AUTOEXEC.BAT. Check for hardware conflicts. Make sure that there are no other hardware devices in the system that may be conflicting with the CD-ROM drive controller. If problems persist, replace the drive controller.

Symptom 10-23. The LCD on your CD-ROM displays an error code. Even without knowing the particular meaning of EVERY possible error message, you can be assured that most CD-based error messages can be traced to the following causes (in order of ease):

• Bad caddy. The CD caddy is damaged or inserted incorrectly. The CD may also be inserted into the caddy improperly.
• Bad mounting. The drive is mounted improperly, or mounting screws are shorting out the drive’s electronics.
• Bad power. Check the +12 and +5 volts powering the CD-ROM drive. Low power may require a new or larger supply.
• Bad drive. Internal diagnostics have detected a fault in the CD-ROM drive. Try replacing the drive.
• Bad drive controller. Drive diagnostics have detected a fault in the drive controller. Try replacing the drive controller or SCSI adapter (whichever interface you’re using).

Symptom 10-24. When a SCSI CD-ROM drive is connected to a SCSI adapter, the system hangs when the SCSI BIOS starts. In most cases, the CD-ROM drive supports plug-and-play, but the SCSI controller’s BIOS does not. Disable the SCSI BIOS through a jumper on the controller (or remove the SCSI BIOS IC entirely) and use a SCSI driver in CONFIG.SYS instead. You may need to download a low-level SCSI driver from the adapter manufacturer.

Symptom 10-25. You see an error such as; "Unable to detect ATAPI IDE CD-ROM drive, device driver not loaded". You have a problem with the configuration of your IDE/EIDE controller hardware. Check the signal cable first, and make sure that the 40-pin signal cable is attached properly between the drive and controller. IDE CD-ROM drives are typically installed on a secondary 40-pin IDE port. Make sure that there is no device in the system using the same IRQ or I/O address as your secondary IDE port. Finally, make sure that any command line switches for the low-level driver in CONFIG.SYS correspond to the controller’s hardware settings.

Symptom 10-26. The CD-ROM drive door will not open once the 40-pin IDE signal cable is connected. You should only need power to operate the drive door. If the door stops when the signal cable is attached, there are some possible problems to check. Check the power connector first, and make sure that both +5 and +12 volts are available at the power connector. See that the power connector is attached securely to the back of the CD-ROM drive. Check the IDE signal cable next - the 40-pin signal cable is probably reversed at either the drive or controller. Try a different signal cable. Also make sure that the 40-pin IDE drive is plugged into a "true" IDE port - not a proprietary (non-IDE 40-pin) port. If problems persist, try a known-good CD-ROM drive.

Symptom 10-27. You are using an old CD-ROM and can play CD audio, but you cannot access directories or other computer data from a CD. Older proprietary CD-ROM drives often used two low-level drivers - one for audio, and one for data - you probably only have one of the drivers installed. Check your low-level drivers first, and see that any necessary low-level drivers are loaded in the CONFIG.SYS file. Also see that any command line switches are set properly. Some older sound boards with integrated proprietary CD-ROM drive controllers may not work properly with the drivers required for your older CD-ROM drive. You may have to alter the proprietary controller’s IRQ, DMA, or I/O settings (and update the driver’s command line switches) until you find a combination where the driver and controller will work together.

Symptom 10-28. The front panel controls of your SCSI CD-ROM drive do not appear to work under Windows 95. Those same controls appear to work fine in DOS. Windows 95 uses SCSI commands to poll removable media devices every two seconds in order to see if there has been a change in status. Since SCSI commands to the CD-ROM generally have higher priority than front panel controls, the front panel controls may appear to be disabled under Windows 95. Try pressing the front panel controls repeatedly. You may be able to correct this issue by disabling the CD-ROM polling under Windows 95.

Symptom 10-29. You cannot change the CD-ROM drive letter under Windows 95. You need to change the drive’s settings under the Device Manager:

• Open the Control Panel and select the System icon.
• Once the System Properties dialog opens, click on the Device Manager page.
• Locate the entry for the CD-ROM. Click on the "+" sign to expand the list of CD-ROM devices.
• Double-click on the desired CD-ROM.
• Once the CD-ROM drive’s Properties dialog appears, choose the Settings page.
• Locate the current drive letter assignment box and enter the new drive designation. Multiple letters are needed only when a SCSI device is implementing LUN addressing (i.e. multidisc changers).
• Click on the OK button to save your changes.
• Click on the OK button to close the Device Manager.
• A System Settings Change window should appear. Click on the Yes button to reboot the system so that the changes can take affect, or click on the No button so that you can make more changes to other CD-ROMs before rebooting system. Changes will not become effective until the system is rebooted.

Symptom 10-30. You installed Windows 95 from a CD-ROM disc using DOS drivers, but when you removed the real-mode CD-ROM drivers from CONFIG.SYS, the CD-ROM no longer works. You need to enable protected-mode drivers by running the Add New Hardware wizard from the Control Panel:

• Boot Windows 95 using the real-mode drivers for your CD-ROM and its interface.
• Open the Control Panel and select the Add New Hardware icon.
• Proceed to add new hardware, but do NOT let Windows 95 attempt to "auto-detect" the new hardware. Use the diskette with protected-mode drivers for the new installation.
• When the new software is installed, Windows 95 will tell you that it must reboot before the hardware will be available - do NOT reboot yet.
• Open a word processor such as Notepad, and edit the CONFIG.SYS and AUTOEXEC.BAT files to REMark out the real-mode drivers for your CD and the reference to MSCDEX.
• Shut down Windows 95, then power down the system.
• Check to be sure that the CD-ROM interface is set to use the resources assigned by Windows 95.
• Reboot the system - your protected-mode drivers should now load normally.

Symptom 10-31. Your CD-ROM drive’s parallel port-to-SCSI interface worked with Windows 3.1x, but does not work under Windows 95. This problem is typical of the NEC CD-EPPSCSI01 interface, and is usually due to a problem with the driver’s assessment of your parallel port type (i.e. bi-directional, unidirectional, or enhanced parallel port). Start your CMOS Setup routine first and see what mode your parallel port is set to operate in. Make sure it is set to a mode which is compatible with your parallel port drive. Next, update your version of MSCDEX. Change the MSCDEX command line in AUTOEXEC.BAT to load from the C:\WINDOWS\CONTROL\ directory, and remove the /L:x parameter from the end of the MSCDEX command line (if present). Finally, cold boot the computer. Since typical parallel port-to-SCSI interfaces get their power from the SCSI device, the external drive must be powered up first. If you’re using real-mode drivers for the interface, place a switch at the end of the interface’s command line that tells the driver what mode your parallel port is operating in. For example, the Trantor T358 driver (MA358.SYS) uses the following switches (yours will probably be different):

• /m02 ;for unidirectional mode (also known as "standard" or "output only")
• /m04 ;for bi-directional mode (also known as PS/2 mode)
• /m08 ;for enhanced mode

As an alternative, disable your real-mode drivers. Remove or REMark out any references to the interface’s real-mode drivers in CONFIG.SYS, then remove or disable the MSCDEX command line in AUTOEXEC.BAT. Start Windows 95, open the Control Panel, select the System icon, then choose the Device Manager page. Find the SCSI adapter settings and expand the "SCSI Controllers" branch of the device tree. Select the device identification line for your parallel port-to-SCSI interface, then click on the Properties button. Click on the Settings page. In the Adapter Settings dialog box, type in the same parameter that would have been used if you were using real-mode drivers. Click on the OK buttons to save your changes, then select Yes to reboot the system. If problems persist, check the technical support for your parallel port-to-SCSI adapter and see if there are any known problems with your particular setup, or any updated drivers available for download.

Symptom 10-32. You see a message that the; "CD-ROM can run, but results may not be as expected". This simply means that Windows 95 is using real-mode drivers. If protected-mode drivers are available for the CD-ROM drive, you should use those instead.

Symptom 10-33. The CD-ROM works fine in DOS or Windows 3.1x, but sound or video appears choppy under Windows 95. There are several factors that can effect CD-ROM performance under Windows 95. Windows 95 performance (and stability) is severely degraded by real-mode drivers, so start by removing or disabling any real-mode drivers. Try installing the protected-mode drivers for your CD-ROM drive instead. If protected-mode drivers are not available for your drive, you may consider upgrading the CD-ROM hardware.

Also avoid using DOS or Windows 3.1x applications under Windows 95. Real-mode applications run under Windows 95 can also cripple performance. Try exiting any DOS or Windows 3.1x applications that may be running on the Windows 95 desktop. Also exit unneeded Windows 95 applications since additional applications take a toll on processing power. Try exiting any Windows 95 applications that may be running in the background. Finally, try rebooting the system to ensure that Windows 95 has the maximum amount of resources available before running your CD-ROM application.

Symptom 10-34. You can't read a Video CD-I disc in Windows '95 using any ATAPI/IDE CD-ROM drive. The built-in ATAPI driver in Windows '95 cannot read raw data in 32-bit disk access mode. Note that such symptoms can also happen to any ATAPI/IDE compatible CD-ROM as long as they are using the built-in ATAPI driver in Windows '95. You should update the CD-ROM’s ATAPI driver to a current manufacturer-specific version. As another alternative, you can use the following procedure:

1. Disable 32-bit disk access feature of Windows '95.
2. Under the Windows '95 desktop, click Start and choose Settings and Control Panel.
3. Click on System icon and select the Performance option.
4. Choose File System and select the Troubleshooting option.
5. At the Troubleshooting dialog, click on "Disable all 32-bit disk access".
6. Edit AUTOEXEC.BAT and append the following line (where {path} is the path name of your Windows '95 software):

C:\{path}\COMMAND\MSCDEX.EXE /D:MSCD000

Symptom 10-35. An IDE CD-ROM is not detected on a 486 PCI motherboard. This is a known problem when using Aztech CD-ROM drives and 486 PCI motherboards with SIS 82C497 chipsets. The motherboard bus noise is far too high, and this results in the misinterpretation of the IDE interface handshaking signals (namely DASP,PDIAG). As a consequence, the CD-ROM drive sometimes (or always) is not detected. You may be able to resolve this problem by connecting the IDE CD-ROM drive as a "slave" device to the hard disk - though you may need to slow the hard drive’s data transfer mode to accommodate the slower CD-ROM drive.

Symptom 10-36. An IDE CD-ROM is not detected when "slaved" to an IBM hard drive. This is a known problem with Aztech IDE CD-ROM drives and IBM Dala 3450 hard drives. The pulse width for the drive detection signal (DASP) is not long enough for the CD-ROM to identify itself properly. This results in the improper detection of an Aztech IDE CD-ROM. You should make the CD-ROM drive a master device on its own IDE channel, or (if possible) upgrade the CD-ROM drive’s firmware to utilize more reliable timing. If the CD-ROM manufacturer has no firmware upgrades available, and you cannot reconfigure the CD-ROM on another IDE channel, you’ll need to replace the CD-ROM or hard drive.

Symptom 10-37. The CD-ROM drive will not read or run CD Plus or Enhanced CD titles. This is a known problem with Acer CD-ROM models; 625A, 645A, 655A, 665A, 525E, 743E, 747E, and 767E. The CD Plus (or Enhanced CD) titles use a new data format recently released by Sony. The new format is for interactive CD titles that incorporate video clips and music, and the data structures on these CDs are cannot be recognized by these CD-ROM drive models. In this case, you’ll need to upgrade the CD-ROM drive outright to a newer model which CAN accommodate newer file types.

Symptom 10-38. You notice that the LED indicator on the CD-ROM is always on. The drive seems to be working properly. This is not necessarily a problem. Some CD-ROM drive models (such as the Acer 600 series) use the LED indicator as a "READY" light instead of as a "BUSY" light. Whenever a CD is loaded in the drive, the LED will be lit, and will remain lit whether the drive is being accessed or not. This feature tells the user whether or not a CD-ROM disc is currently loaded in the drive by simply checking the LED. There may be a jumper on the CD-ROM drive that allows you to switch the indicator light from "Ready" mode to "Busy" mode.

Symptom 10-39. You cannot play CD-audio on a particular CD-ROM under Windows 95. Replacing the CD-ROM resolves the problem. This is a known incompatibility issue with Acer 525E CD-ROM drives and Windows 95 (this does not effect the integrity of programs and data). Windows 95 will mute the CD-audio on this and many other brands of double speed IDE CD-ROMs. If you cannot obtain a patch directly from Microsoft or the CD-ROM manufacturer, your only real alternative is to replace the CD-ROM drive.

Prices for CD recorders (or CD-Rs) have tumbled over the first half of 1997 - recorders which would have cost thousands of dollars just a couple of years ago can now be purchased for just $400-$600 (US). These low prices, combined with readily available units from Philips, Sony, Hi-Val, Smart and Friendly, and other manufacturers, means that CD-Rs have begun appearing in desktop and tower systems. CD recorders offer some exciting potentials for computer users. Not only are CD-Rs ideal for file backup and archiving purposes, but CD-Rs support data-intensive uses like photo albums, personal clipart libraries, customized multimedia productions, and high-volume file distribution.

However, CD recorders present some special problems for the typical PC. Virtually all CD-R units use the SCSI interface in order to handle more consistent data transfer from the system to the drive. Installing a CD-R may require the addition (and expense) of a SCSI adapter and driver software. CD recording demands a substantial commitment of hard drive space - perhaps as much as 1GB - in order to create an image file for recording (an "image file" basically converts the data to be recorded into the "pits" and "lands" that must be encoded to the blank disc). So if you’re tight on drive space, you may also need another hard drive to support the CD-R. Finally, CD-Rs require a constant and uninterrupted flow of data during the recording process. If the CD-R data buffer empties, the recording process will halt, and your blank CD will be ruined. This means you’ll need fast hard drives and a high-performance interface (i.e. PIO Mode 4). This part of the chapter explains some of the problems associated with installing and using a CD-R, and illustrates a series of troubleshooting symptoms and solutions.

Writing data to recordable compact disc is a complex process that demands a great deal from your PC’s hardware and software - most of this complexity is hidden by the power of the CD authoring program, but there are a number of important factors that you should be aware of which can influence the success of CD recording.

File sizes - The sheer amount of data being written to the CD is less important than the individual file sizes - the recorder may have trouble locating and opening the files quickly enough to send them smoothly to the CD recorder, where fewer large files are typically problem-free.

System interruptions - Any interruption in the flow of data is fatal to CD recording, so make sure that your CONFIG.SYS and AUTOEXEC.BAT files do not load any TSR utilities which may periodically interrupt the computer’s drive operations. Utilities like screen savers, calendar alarms or reminders, and incoming faxes are just a few "features" which will interrupt disc writing. If the PC is part of a network, you should temporarily disable network sharing so that no one tries to access the files you're trying to write to the CD.

The hard disk - The hard drive is a critical component of the CD-R system because you must create a sizable "image file" which will then be sent to the CD-R. There are three major issues when considering your hard drive: speed, file fragmentation, and thermal calibration.

• Speed - in order to write a virtual "image file" to a compact disc, the hard disk from which you are writing must have a transfer rate fast enough to keep the CD-R drive buffer full. This usually means an average hard disk access time of 19ms or less. It would also help to use a high-performance drive interface such as EIDE or SCSI-2.
• Fragmentation - this issue is also related to speed. Searching all over a very fragmented hard disk for image file data can cause drive operations to slow down. In many cases, a badly fragmented hard drive cannot support CD-R operations. Be sure to defragment your hard drive before creating an image file.
• Thermal calibration - all hard disks periodically perform an automatic thermal calibration to ensure proper performance. Calibration interrupts hard disk operations for as much as 1.5 seconds. Some hard disks force a calibration at fixed intervals (even if the disk is in use) causing interruptions which are fatal to CD writing. This problem is particularly noticeable when the image file is large, and the writing process takes longer. If you can select a new hard drive to support CD-R operations, choose a drive with "intelligent" thermal calibration which will postpone recalibration until the drive is idle.

CD recorder speed - Many current CD recorders are capable of writing at 2x or 4x the standard writing/playback speed of 150KB/s (75 sectors/s). Recording speed is simply a matter of how fast the bits are inscribed by the laser on the disc surface, and has nothing to do with how fast you read them back or how much data you can fit on the disc, however, higher recording speeds can accomplish a writing process in a shorter period of time. Faster recording speeds are certainly a time saver, but it also means that larger recording buffers are required (and those buffers empty faster). As a consequence, faster recorders will demand a faster hard drive and interface to support data transfer. In most cases, "buffer underrun" type problems can often be corrected by slowing down the recording process rather than upgrading the drive system.

When you write a real ISO image file from hard disk to CD, speed is rarely a problem because the image is already one gigantic file in which the files and structures are already in order and divided into CD-ROM sectors, so it is only necessary to stream data off the hard drive to the CD recorder. When you write from a "virtual" image, things get trickier because a "virtual" image is little more than a list. The CD authoring program must consult the virtual image database to find out where each file should go in the image and where each file is actually is stored on hard disk. The authoring software must then open the file and divide it into CD-ROM sectors - all while sending data to the CD recorder in a smooth, continuous stream. Locating and opening each file is often the more time-consuming part of the recording process (which is why "on-the-fly" writing is more difficult when you have many small files).

CD recorder buffer - All CD recorders have a small amount of on-board buffer memory. The CD recorder's buffer helps to ensure that there is always data ready to be written because extra data is stored as it arrives from the computer. The size of the buffer is critical to trouble-free writing - a slow-down or interruption in the transfer of data from the computer will not interrupt writing so long as the buffer is not completely emptied. The larger the buffer, the more safety margin you have in case of interruptions. If your CD recorder has a very small buffer and your hard disk is slow, you may find it difficult (or impossible) to write virtual images on-the-fly to CD. When this occurs, you can make a real ISO image file on the hard disk and record to CD from that, use a faster hard disk sub-system, or upgrade your CD recorder’s buffer (if possible).

NOTE: If you want to write a virtual image "on-the-fly" to CD, and you have a slow hard disk, it is generally safest to write at 1x speed. Otherwise, create a real ISO image file first and record from that. In most situations where your hardware configuration is adequate (a fast, defragmented hard disk, few small files, and a good-sized CD recorder buffer), you can successfully write virtual images straight to CD. However, it's always best to test first, and create a real ISO image file only if necessary.

Even when CDs record perfectly, it is not always possible to read them correctly in other drives. The following notes highlight three common compatibility issues.

Problems reading recordable CDs - Recordable CDs frequently cannot be read in ordinary CD-ROM drives. If the CD can be read when used on the CD-R but not on a standard CD-ROM drive, check in disc recording utility to make sure that the session containing the data you just wrote is closed - CD-ROM drives cannot read data from a session which is not closed.

If your recorded disc is ejected, you receive an error message, or you have any random problems accessing files from the recorded disc, the problem may be that your CD-ROM drive is not well calibrated to read recorded CDs. Try the disc on another CD-ROM drive.

If you recorded the disc using DOS filenames, but there are difficulties in reading back the recorded CD with DOS or Windows, it may be that you have an older version of MSCDEX (before version 2.23) on your system. Check your MSCDEX version, and update it if necessary.

Problems reading multisession CDs - If you can only see data recorded in the first session on the CD - but not in subsequent sessions - it may be that the disc was recorded in CD-ROM (Mode 1) format, while your multi-session CD-ROM drive only recognizes CD-ROM XA (Mode 2) multi-session CDs. If this happens, you may need to re-record the disc in the correct mode. Of course, your CD-ROM drive must support multi-session operation in the first place. If you can only see data recorded in the last session, you may have forgotten to link your new data with data previously recorded on the CD. Refer to the instructions for your CD recorder and review the steps required to create a multi-session CD.

CD-ROM drive incompatibility with recordable CDs - Sometimes, it seems that you wrote a CD without trouble and can read it properly on your CD-R, but when you put the disc in a standard CD-ROM drive, the disc is ejected, or you see error messages such as "No CD-ROM" or "Drive not ready", or you have random problems accessing some files or directories. You may also find that the problems disappear when reading the CD on a different CD-ROM drive.

At first, you may suspect a problem with the original CD-ROM drive, but this may be due to compatibility problems with some CD-ROM drives (especially older ones) and recorded CDs. Some CD-ROM drive lasers are not calibrated to read recordable CDs (often the surface is different from that of factory-pressed CDs). If your CD-ROM drive reads mass-produced (silver) CDs but not recordable CDs, check with the CD-ROM drive manufacturer to determine whether this is the problem. In some cases, a drive upgrade may be available which will resolve the problem.

NOTE: The combination of blank disc brand and CD recorder can also make a difference. Use blank CD media which has been recommended by the CD-R manufacturer.

CD recorders are subject to a large number of potential errors during operation. Many typical recording errors are listed below. In most cases, the error is not terribly complex, and can be corrected in just a few minutes once the nature of the problem is understood. Keep in mind that the actual error message is dependent on the CD recorder software in use, so your actual error messages may vary just a bit.

Symptom 10-40. Absorption control error <xxx>. This error most often means that there is a slight problem writing to a recordable disc - perhaps caused by a smear or speck of dust. It does not necessarily mean that your data has not been correctly recorded. A sector address is usually given so that you can (if you wish) verify the data in and around that sector. When writing is completed, try cleaning the disc (on the non-label side) gently with a lint-free cloth. If the error occurs again, try a new disc.

Symptom 10-41. Application code error. This error typically occurs when you try to write Kodak recordable CDs (Photo CDs) on non-Kodak CD recorders. These discs have a protection bit which is recognized only by the Kodak CD-R - all other recorders will not record these discs. In this case, you’ll need to use "standard" blank CDs.

Symptom 10-42. Bad ASPI open. The CD-R ASPI driver is bad or missing, and the SCSI CD-R cannot be found. Check the installation of your CD-R drive and SCSI adapter, then check the driver installation. Try reinstalling the SCSI driver(s).

Symptom 10-43. Buffer underrun at sector <xxx>. Once an image file is generated, CD writing is a real-time process which must run constantly at the selected recording speed - without interruptions. The CD recorder's buffer is constantly filled with data from the hard drive waiting to be written. This "buffering" action ensures that small slowdowns or interruptions in the flow of data from the computer do not interrupt writing.

The "buffer underrun" message indicates that the flow of data from hard disk to CD recorder was interrupted long enough for the CD recorder's buffer to be emptied, and writing was halted. If this occurs during an actual write operation rather than a test, your CD may be damaged.

To avoid buffer underruns, you should remove as much processing load as possible from the system. For example, make sure that no screen savers or other Terminate and Stay Resident (TSR) programs are active (they can momentarily interrupt operations). Close as many open windows as possible. See that your working hard disk cannot be accessed via a network.

Also, the CD recorder's position in the SCSI chain - or the cable length between the computer and CD recorder - may cause data slowdowns. Try connecting the CD recorder as the first peripheral in the SCSI chain (if not done already), and use a shorter SCSI cable (if possible) between the CD recorder and the SCSI host adapter.

Symptom 10-44. Current disc already contains a closed audio session. Under the Red Book standard for audio CDs, all audio tracks must be written in a single session. If you add audio tracks in more than one session, playback results will be unpredictable. Most CD-ROM drives will playback all audio tracks on a CD even if they are recorded in several different sessions, but most home and car CD players can only playback the tracks in the first session. If you continue and record audio in a different session, you may have problems reading subsequent audio sessions.

Symptom 10-45. Current disc contains a session that is not closed. In actual practice, CD-ROM drives can only read back one data track per session, so avoid recording another data track in an open session. Be sure to close the session before writing additional data to the disc.

Symptom 10-46. Currently selected source CD-ROM drive or CD recorder cannot read audio in digital format. This is more of a warning than a fault. Reading audio tracks in "digital format" is not the same as playing the music, and few CD-ROM drives are able to read audio tracks in digital format (only Red Book format).

Symptom 10-47. Data overrun/underrun. The SCSI host adapter has reported an error which is almost always caused by improper termination or a bad SCSI cable. Recheck the installation of your SCSI adapter, cabling, and termination.

Symptom 10-48. Destination disc is smaller than the source disc. This error commonly occurs when you’re trying to duplicate an existing CD to the CD-R. There is not enough room on the recordable CD to copy the source CD. Try recording to a blank CD. Use 74-minute media instead of 60-minute media. Some CDs cannot be copied due to the TOC (Table of Contents) overhead in CD recorders, and also due to the calibration zone overhead.

Symptom 10-49. Disc already contains tracks and/or sessions that are incompatible with the requested operation. This error appears if you are trying to add data in a format which is different from the data format already on the disc. For example, you’ll see this type of error when trying to add a CD-ROM XA session to a disc that already contains a standard CD-ROM session. A disc containing multiple formats is unreadable, so you are not allowed to record the different session type.

Symptom 10-50. Disc write-protected. You are attempting to write to a disc which has already been closed. Do not try writing to discs which are closed. Use a fresh blank disc for writing.

Symptom 10-51. Error 175-xx-xx-xx. This error code often indicates a "buffer underrun". See the first symptom above.

Symptom 10-52. Error 220-01-xx-xx. This error code often indicates that some of your software cannot communicate with a SCSI device - possibly because your SCSI bus was reset. In many cases, this is caused by conflicts between real-mode and protected-mode SCSI drivers working in a Windows 95 system. Try REMming out any real-mode SCSI drivers in your CONFIG.SYS file (the protected-mode drivers provided for Windows 95 should be sufficient on their own).

Symptom 10-53. Error 220-06-xx-xx. This error code often indicates a SCSI Selection Time-out error which indicates a SCSI setup problem - usually with the SCSI host adapter. Contact your SCSI host adapter manufacturer for detailed installation and testing instructions.

Symptom 10-54. Error reading the Table of Contents (TOC) or Program Memory Area (PMA) from the disc. This recordable disc is defective, or has been damaged (probably during a previous write operation). Do not try and write to this disc. Unfortunately, there is very little you can do here except to discard the defective disc.

Symptom 10-55. General protection fault. This type of problem has been identified with the Adaptec AHAr-152x family of SCSI host adapters, and is caused by outdated driver software. You can solve this problem by upgrading to version 3.1 or later of Adaptec's EZ-SCSI software. If you’re not using Adaptec software, check for current drivers for whatever adapter you’re using.

Symptom 10-56. Invalid logical block address. This error message usually means that the CD mastering software has requested a data block from the hard disk which either does not exist or is illegal - this may suggest a corrupted hard disk. Exit the CD mastering software and run ScanDisk and Defrag to check and reorganize your hard drive.

Symptom 10-57. Last two blocks stripped. This message appears when copying a track to hard disk if the track you are reading was created as multi-session compliant (following the Orange Book standard). This is because a multi-session track is always followed by two run-out blocks. These are included in the count of the total size (in blocks) of the track, but do not contain data and cannot be read back. This message appears to alert you just in case you notice that you got two blocks fewer than were reported for the Read Length. Don't panic - you haven’t lost any data.

Symptom 10-58. "MSCDEX" errors are being encountered. Early versions of MSCDEX (prior to v.2.23) had problems with filenames containing "illegal" ASCII characters such as a hyphen. If a directory contains a filename with an "illegal" ASCII character, you can still see all the files by doing a directory (DIR) from DOS, or you can open the illegally-named file. However, one or more files listed after the illegal one may not be accessible or may give errors. You should update MSCDEX to the latest available version.

Symptom 10-59. MS-DOS or Windows cannot find the CD-R drive. There are several possible reasons why the CD-R drive cannot be found by software. First, turn the computer off and wait at least 15 seconds. Make sure the SCSI adapter card is firmly seated and secured to the computer case. The SCSI adapter must also be properly configured. Check the SCSI cable and see that it is properly attached to the adapter and drive. Turn the computer on. If problems persist, make sure that the correct SCSI drivers are installed, and that any command line switches are set correctly.

Symptom 10-60. No write data (buffer empty). The flow of data to the CD-R drive must be extremely regular so that its working buffer is never empty when it prepares to write a block of information to disc. This message indicates that the flow of data from the hard disk to the CD recorder has been interrupted (similar to the "Buffer underrun" error). Ensure that no screen savers, other TSR utilities, or unneeded open windows are active which might momentarily interrupt operations. Your working hard disk should not be accessible over a network.

The CD recorder's position in the SCSI chain, or the length of cabling between the SCSI adapter and CD recorder may also cause data slowdowns. Try connecting the CD recorder as the first device in the SCSI chain (you may need to re-terminate the SCSI chain), and keep the SCSI cable as short as possible.

Windows 3.1x requires the use of a RAM cache to manage the flow of data. SmartDrive (the caching utility supplied with Windows 3.1x) is necessary for writing virtual images on-the-fly to CD. However, when writing a real ISO image from hard disk to CD, it may cause a buffer underrun. If a buffer underrun occurs during testing or writing of a real ISO 9660 image under Windows 3.1x, exit to the DOS shell and type the following:

smartdrv x-

where x is the letter of the hard drive from which you will write the ISO image. This disables SmartDrive for the specified drive so that CD writing can proceed smoothly.

Symptom 10-61. Read file error. A file referenced by the virtual image database cannot be located or accessed. Make sure that the suspect file is not being used by you or by someone else on a network.

Symptom 10-62. Selected disc image file was not prepared for the current disc. This type of error message occurs if you prepared the disc image file for a blank CD, but are now trying to record it to a CD already containing data, (or vice versa). In either case, you would wind up writing a CD that couldn’t be read at all because the CD addresses calculated for the disc image are wrong for that actual CD. If you are given the option of writing anyway, select "No" to abort because it is very unlikely that the writing operation would yield a readable CD.

Symptom 10-63. Selected disc track is longer than the image file. The disc verify process fails immediately because the source ISO 9660 image file and the actual ISO 9660 track on CD are not the same size - the disc track is actually longer than the image file, and could indicate a defective CD-R drive.

Symptom 10-64. Selected disc track is shorter than the image file. The disc verify process fails immediately because the source ISO 9660 image file and the actual ISO 9660 track on CD are not the same size - the disc track is actually shorter than the image file, and could indicate a defective CD-R drive.

Symptom 10-65. The "disc in" light on the drive does not blink after you turn on the computer. In virtually all cases, there is no power reaching the CD-R drive. For internal CD-R drives, make sure the computer's 4-pin power cable is properly connected to the CD-R drive unit. For external CD-R drives, make sure the power cord is properly connected to the back of the CD-R drive unit, and is plugged in to a grounded power outlet. Make sure the power switch on the back of the drive is ON. Refer to your CD-R drive’s Installation Guide for more detailed information.

Symptom 10-66. Write emergency. This error occurs if the drive is interrupted during a write action. It is commonly seen when writing Red Book audio, but can also occur with data. For example, one typical reason for a write emergency is dust particles that cause the laser to jump off track.

Symptom 10-67. The CD-R is recognized by Windows 95, but it will not function as a normal CD-ROM drive. The drive appears normally in the Windows 95 Device Manager. The driver which is operating the CD-R drive may not allow the drive to function as a normal CD-ROM reader. For example, this is a known problem with the Philips CDD2000 CD-R. Check to see if there is an updated Windows 95 CD-R driver which can overcome this limitation. If not, you may need to replace the CD-R drive with an upgraded model whose drivers do support CD-ROM-type functionality.

Symptom 10-68. You cannot read CD-R (gold) discs in some ordinary CD-ROM drives. This is actually a very complex issue because there are a number of important factors which effect the way in which a CD is read. Laser calibration plays a big role. Some CD-ROM drive lasers are not calibrated to read recordable discs (whose recorded surface is slightly different from that of "pressed" discs). If your CD-ROM drive reads mass-produced (silver) CDs but not recordable CDs, check with the CD-ROM drive manufacturer to determine whether laser calibration is the problem. You may be able to return the CD-ROM drive for factory recalibration, or replace the CD-ROM drive with a model that is better calibrated for reading both CD-ROM and CD-R discs.

Fast CD-ROM drive operations may be another problem. In order for some CD-ROM models to work as fast as they do, they must perform unconventional operations such as a laser calibration in the lead-out area to determine the approximate position of several tracks. With some CD recorders, the session lead-out is not recorded correctly, and this can cause problems with gold disc compatibility.

The CD-R authoring software can be a problem. Any authoring software can sometimes produce incorrect tracks due to bugs or recording glitches. A good way to check whether incompatibility problems lie with the originating software is to test the same gold disc on several CD-ROM drives. If one drive is capable of reading the gold disc back correctly, chances are that the problem was not in the recording process.

Finally, consider your version of MSCDEX. Although MSCDEX (the Microsoft extension for reading CD-ROMs) will allow non-ISO legal characters in filenames, versions of MSCDEX prior to 2.23 have a problem in dealing with filenames which contain the hyphen. If a directory contains a filename with a hyphen in it, you will be able to see all the files by doing a DIR from DOS. But any files listed after the file with the illegal name are not accessible - when trying to open them, you would get a "file not found" message. MSCDEX 2.23 appears to have fixed this bug.

This concludes Chapter 10. Be sure to review the glossary and chapter questions on the accompanying CD. If you have access to the Internet, point your web browser to some of the contacts below:

AcerOpen: http://www.acercomponents.com/POL_CD-Drives.htm

Adaptec: http://www.adaptec.com/cdrec/ (CD Creator 2.x and Adaptec's Easy CD Creator Deluxe 3.0)

Aztech: http://www.aztech.com.sg/c&t/spec_cd.htm

CDR Publisher: http://www.cdr1.com

CeQuadrat: http://www.cequadrat.com/ (WinOnCD 3.0 software)

El Torito specification: http://www.ptltd.com/techs/specs.html

Philips: http://www.pps.philips.com

Smart and Friendly: http://www.smartandfriendly.com

Teac America: http://www.teac.com/dsp/dsp.html

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