Overview of the IDE Interface

7-1: FYI

The Integrated Drive Electronics ( IDE ) is the primary interface used to connect a hard disk drive to a PC and refers to the fact that the interface electronics or controller is built into the drives themselves, these include CD-ROM, DVD, CD/RW, high-capacity floppy and tape drives. The IDE connector on motherboards in many systems is nothing more than a stripped down bus slot. In ATA IDE installations, these connectors normally contain a 40-pin subset of the 98 pins that would be available in a standard 16-bit ISA bus slot.

7-2: ATA / ATAPI-5

Copies of any of the published standards can be purchased from ANSI or Global Engineering Documents. ATA-5 includes ultra-ATA/66, which doubles the ultra-ATA burst transfer rate by reducing set-up times and increasing the clock rate. The faster clock rate increases interference, which causes problems with the standard 40-pin cable. To eliminate noise and interference, a new 40-pin, 80-conductor cable was developed. This cable was first announced in ATA-4, but now is mandatory in ATA-5 to support the ultra-ATA/66 mode. This cable adds 40 additional ground lines between each of the original 40 ground and signal lines, which help shield the signals from interference. This cable will work with older non-ultra-ATA devices as well. The new cable will support the Cable Select feature and have color coded connectors. The blue end connector should be connected to the ATA host interface (usually the motherboard). The black opposite end connector is known as the Master position, which is where the primary drive will plug in. The gray middle connector is for the Slave position.

7-3: Why not CD/RW and Hard drive on same Channel

When only one drive is installed, the controller responds to all commands from the system. When two drives and therefore two controllers are installed all commands from the system are received by both controllers. Each controller then must be set up to respond only to commands for itself, thus Master / Slave. Most CD-ROM, Tape Drives, DVD and CD/RW run at lower IDE mode speeds, this would force your hard disk to run slower if they shared a single cable. IDE does not normally support overlapping access such as SCSI, basically, when one drive is running the other can not be accessed. By keeping them on separate channels, you can more effectively overlap accessing between them. This is why in a system with 4 devices, that includes a Zip drive, the Zip is connected to Pri IDE as slave, it can not support the transfer rate and should never be in use while the CD/RW is in the "burn" process.

7-4: A word about SCSI and IDE: ( author; VinTek )

A couple of years ago, I would have told you to make sure that your CD-ROM and CD-RW drives were on separate channels. This was because EIDE drives were notoriously unreliable in managing I/O tasks on the same channel. You would get buffer underruns and the result would be a coaster. Recently, however, CD-RW drives have improved to the degree (through larger buffers and other such improvements) that many people, including myself, routinely install both drives on the secondary channel.

However, you still have EIDE drives, which in turn means that your CPU is handling the I/O chores. CD-RW drives have improved to the point where buffer underruns are much less frequent than they used to be, but you'll still risk a coaster if you try to do too much while burning a CD. The load on the CPU would distract it from the burn, and boom! Buffer underrun. That is why most of us recommend that you turn off all unrelated programs, such as antivirus utilities and screensavers, while burning a CD. I go the extra mile by creating a fixed swap drive so that Windows does not try to resize it during the burn.

This brings us to SCSI. Because of the improvement in IDE drives, SCSI doesn't hold as much of an advantage as it used to, but it's still the closest you can get to having bulletproof burns. This is because the SCSI controller chip takes over the job of managing the I/O tasks from the CPU. I have seen SCSI systems complete a burn through to disk finalization even after a BSOD! That is impressive. With a good SCSI card, you can daisy chain up to 27 devices (cheaper ones max out at about 7). Drawbacks are expense (both in terms of the card and the peripheral) and complexity. There is the bother of having to set the SCSI ID and terminate the last device in the chain. In addition, naturally, if you truly want a bulletproof burn, then both your source and target should be SCSI. This means having to have a SCSI hard drive and SCSI CD-ROM/DVD player.

Is SCSI worth it? If you burn a lot of CDs (maybe you have to back up and archive databases on a regular basis; maybe you're a music fiend and want to custom-mix a lot of audio CDs), then yes, the added reliability is probably worth the money. If you are like most people who just want to back up files and occasionally want to mix a CD for your car, then stick with EIDE.

A word about USB. They are pretty neat. At this point, I have seen them go up to 4X, meaning that you can burn a CD in about 19 minutes. This is in contrast to 8X drives, which will take about 10.5 minutes. There are some 12X drives around, but I have not had any experience with them. Those are CD-R times, by the way. CD-RW times are often, but not always, twice the CD-R times. What you gain is the fact that you do not take up any extra IRQs and you also get portability.

7-5: A brief History on ATA interface, Transfer Modes and Speeds

ATA was original created in form for small-capacity low-cost drives. It has evolved long with the needs of modern PC, higher capacities and faster access times. The standard hard drives in most PC`s use the ATA Attachment interface and now most new CD-ROM / CD-RW drives also use one of the more recent versions of ATA. What makes ATA so appealing is its simplicity, connecting them require only two cables, a signal cable and a power cable. You do not have to worry about RLL data coding, modulation techniques or proper termination.

Around the time Seagate developed Fast ATA, Western Digital sought to strengthen the original ATA standard, Enhanced IDE / EIDE. Later the two groups united, standardization of ATA was developed and approved. All aspects of both Fast ATA and EIDE are now part of the official standard. In 1996 ATA-2 standard, faster transfers became officially sanctioned. In 1998 the packet interface that extended official ATA support to CD / CD-RW drives and other devices was added under ATA-4.

The information available is extensive, but ordinarily you need only be concerned with modes and transfer rates when you are selecting a hard disk drive to match with your PC. In operation your PC`s BIOS will automatically recognize the device and set itself up for the fastest operating mode that it shares with your hard disk drive. Below is a chart showing relevant  Transfer modes and Speeds.

7-6: What is Ultra3 SCSI and some of its advantages?

With the use of LVD (low voltage differential) technology, Ultra3 SCSI provides for cable lengths of up to 12 meters, allowing for multiple drive configurations and hassle-free external device setup. In a single-device channel, cable length can actually be 25 meters.

7-7: What is the new Ultra2 SCSI specification? (Article #990427-0014)

7-8: What is Firmware?

What is firmware?
Firmware is a special-purpose module of low-level (e.g., hexadecimal, machine code) software that serves two purposes. First, it acts like a BIOS, enabling the device to take stock of its capabilities and to render those capabilities functional. Second, it coordinates the activities of the hardware during normal operation and contains programming constructs used to perform those operations. For example, in a typical modem, the firmware will be a factor in establishing the modem's data rate, command set recognition, and special feature implementation.

Firmware is stored in a special type of memory chip that doesn't lose its storage capabilities when power is removed or lost. This non-volatile memory is classified as "read-only" memory (ROM) because the user, during normal operation, cannot change the information stored there. The basic type of chip is called a PROM, which is programmable by any technician who has a programming console. A basic PROM receives one version of firmware. That code is "burned in" to the PROM and cannot be changed. To update the firmware, the PROM must be physically removed from the device and replaced with a new chip.

Flash Capabilities
Improvements on this technology have rendered EPROM, PEROM, and EEPROM chips, which are variations of the PROM that are erasable using either UV-light (e.g., the origin of the term "flashable") or electrical energy.