One of the key appeals to the IBM-type personal computer architecture is its functional modularity - its ability to accept a variety of expansion devices such as modems, video controllers, drive adapters, video capture/TV boards, and so on. Each device added to a system needs to be "configured" in order to utilize unique IRQ, DMA, and I/O resources. Traditionally, devices were configured manually using a series of jumpers on the device. While this proved to be a straightforward approach, it also opened the way for many configuration conflicts (devices accidentally configured to use overlapping resources). Reporting utilities are also imprecise, making conflict resolution somewhat of a tedious, "hit-and-miss" process. Current operating systems typically provide better tools for conflict resolution (see Chapter 13), but resolving conflicts still demands a certain amount of patience and expertise.

Designers have long sought to "automate" this device configuration process, removing the error-prone task of device configuration from the hands of end-users and busy technicians. The results of this "automatic configuration" technology has become known as Plug-and-Play (or PnP). First introduced with late-model i486 systems, PnP is now a standard technology implemented in all current PCs. Although PnP simplifies much of the configuration problems with new systems, there are still many situations where PnP doesn’t work perfectly (especially when running devices under DOS, or using pre-PnP devices in a PnP system). This chapter describes the requirements for PnP, outlines the special requirements for implementing PnP under DOS, and provides a series of troubleshooting points.

The first step in troubleshooting plug-and-play is to understand the issues involved in making it run. PnP is not one particular technology, but rather it is a combination of features all brought together. There are three components involved in a PnP system; PnP devices, PnP BIOS, and a PnP-compliant operating system - each part must be PnP-compatible.

A PnP system requires one or more "devices" - the modems, video adapters, chipsets, drive adapters, and myriad other hardware elements in the PC. Ideally, EVERY device in the PC will be PnP-compatible, and today’s systems DO contain virtually all PnP devices. PnP devices are capable of identifying themselves and their resource requirements to the rest of the system. The only wrinkles occur when non-PnP (or "legacy") devices are mixed into the system hardware.

A PnP system requires a PnP BIOS - especially at boot time. Since PnP devices initialize in the inactive state by default, the PnP BIOS is needed to initialize the core PnP devices (i.e. the video adapter and boot drive) in order to complete the POST and launch the operating system. You should also note that the original version of PnP BIOS (version 1.0) was finalized in May 1994. By October 1994, additional clarifications were added. As a consequence, older PnP systems are not fully compliant with the current specification. PnP support problems on older systems can usually be corrected with a BIOS upgrade. System PnP support can typically be enabled or disabled through the CMOS Setup routine.

The PnP OS takes over where the PnP BIOS leaves off by identifying and configuring the remaining PnP devices in the system, then loading the appropriate drivers needed to initialize and operate each respective device. The OS also must keep resources aside for non-PnP ("legacy") devices, and report any changes to the hardware complement in the system. Windows 95 is generally regarded as the premier PnP operating system for end-users and general-purpose PCs, while Windows NT provides PnP support for networked and business systems.

Now that you’ve seen the essential elements of PnP, it’s time to look at how it all works. A PnP system must be robust enough to handle several important functions. The major functions that must be handled by these three PnP components can be summarized as:

• Identification of installed devices - the PnP system must be able to identify each installed device. This requires the device to have a certain amount of on-board intelligence.
• Determination of device resource requirements - based on the device identification, the PnP system must be able to determine the kinds of resources (IRQ, DMA, I/O addresses, or BIOS space) required to support the device.
• Creation of a complete system configuration, eliminating all resource conflicts - after all devices have been identified, and their resource needs evaluated, the PnP system must then allocate the required resources to each device every time the system initializes (without causing a resource conflict).
• Loading of device drivers - after the operating system starts, it then must load the appropriate device drivers needed to support every device in the system.
• Notification of configuration changes - each time a PnP device is added or removed from the PC, the PnP system reports the configuration change. When a device is added, the PnP system attempts to identify it and install the appropriate device drivers. When a device is removed, the PnP system attempts to remove all traces of the device and its drivers.

The PnP system starts with the BIOS at boot time - a certain amount of configuration must first be performed by the system BIOS during system initialization. In order for the system to boot, the PnP BIOS must configure a display device, input device and initial boot device (i.e. video adapter, keyboard, and floppy/hard drives). Then, the PnP BIOS must pass the information about each of these devices to the operating system (i.e. Windows 95) for additional configuration of the remaining system devices.

The operating system then continues the configuration process by identifying every device in the system, and gathering their respective resource requirements. Each non-boot device (i.e. modems, video capture devices) must be inactive upon power-up so that the operating system can identify any conflicts between the resource requirements of different devices before configuring them. When different devices require the same resources, the devices must be able to provide information to the operating system about alternative resource requirements. The operating system then uses initial or alternative requirements to assemble a working system configuration. Once any resource conflicts have been resolved, the operating system automatically programs each hardware device with its working configuration, and then stores all configuration information in the central database contained in ESCD (Extended System Configuration Data) memory which part of CMOS RAM space. Finally, the operating system loads the device drivers for each device, and notifies these drivers of each resource assignment.

If a change occurs to the system configuration during operation (for example, a device is installed or removed), the hardware must be able to notify the operating system of the event so that the operating system can configure the new device. Additionally, applications must be able to respond to configuration changes to take advantage of new devices and to cease calling devices that have been removed. Such dynamic configuration events might include the insertion of a PC Card, the addition or removal of a peripheral such as a mouse, CD-ROM drive, printer, or a docking/undocking event for a notebook computer.

NOTE: In most cases, configuration changes are made before boot time while system power is off. Only PC card and laptop designs support "hot" insertion and removal.

The PnP system is designed to support a wide variety of devices across a number of different bus architectures. In general, there are nine classifications of PnP devices;

• ISA bus cards
• PCI bus cards
• Microchannel (MCA) bus cards
• VESA local bus (VLB) cards
• IDE devices (for hard drives and CD-ROM drives)
• SCSI controllers and devices
• PC Card devices
• Serial port devices (such as modems)
• Parallel port devices (such as printers and parallel port drives)

In order for the PC to recognize and configure a PnP device, each and every device must be able to identify itself and its resource requirements to the system - even motherboard busses and devices must be able to identify themselves. Identification is accomplished through a seven-character code. Each manufacturer is assigned a three-character prefix, the following character identifies the device type, and the remaining three characters identify the particular device. For example, the PnP code PNP0907 identifies a "Western Digital VGA" device adapter. Microsoft reserves the code "PNP" for itself, but other manufacturers are assigned their own codes (i.e. Creative Labs uses the "CTL" prefix). The advantage of Microsoft’s prefixes is that they are "generic", and you can usually identify a device adequately by utilizing the Microsoft generic equivalent. Table 41-1 lists the generic PnP identification categories and codes used by Microsoft.

A. Detection is the process Windows 95 uses during its search for

legacy, or non-Plug and Play, devices on a computer. Detection is

used during Windows 95 Setup and any time you use the Add New

Hardware Wizard to search for new hardware installed in your

computer. Detection does not run each time you start Windows 95.

During the detection process, Windows 95 creates a file called

Detlog.txt in the root directory of the boot drive. This file

exists primarily as a troubleshooting tool.

Enumeration is the process Windows 95 uses to identify Plug and Play

devices in your computer, including those devices on Plug and Play

busses such as ISAPNP, PCI, and PCMCIA (PC card) devices.

Enumeration occurs each time Windows 95 starts and whenever Windows

95 receives notification that a change has occurred in the

computer's hardware configuration, such as when you remove a PCMCIA

card.

Another issue to consider when working with PnP systems is the support of pre-PnP devices (called "legacy" devices). These are the traditional "jumpered" devices which need to be configured manually. Under DOS, legacy devices run just fine and require no special support, but they can cause a problem under Windows 95. Remember that a PnP system relies on the ability to automatically identify each and every device in the system. Since "legacy" devices are not designed to communicate their configuration to the operating system, there is no way for Windows 95 to detect the device - much less assign resources for it. This means Windows 95 can assign resources to a PnP device that are already in use by a legacy device. Windows 95 circumvents this problem by requiring you to "register" legacy devices using the "Add New Hardware" wizard under the Control Panel. Once a legacy device is installed and the system is rebooted, use the Add New Hardware wizard to "tell" Windows 95 about the new device, and install the proper drivers for it.

Now that so many PnP devices are becoming available, a new problem is developing for technicians - PnP support under DOS. While Windows 95 was designed to be a platform for PnP devices, DOS cannot automatically identify and configure PnP devices without additional software drivers. This makes it difficult to use many PnP devices under DOS, but with the proliferation of DOS games and other applications still being developed, PnP support is unquestionably a necessity. In other cases, older hardware platforms may lack the support to fully implement a PnP system (such as older BIOS). This part of the chapter examines the techniques used to implement PnP support under DOS and Windows 3.1x.

If you do not have access to a PnP operating system (i.e. you’re using DOS or Windows 3.1x), you will need to install a PnP configuration driver in CONFIG.SYS which will perform resource allocation and configuration for a PnP device. A PnP configuration driver determines the resource settings of all your system devices and legacy cards, configures PnP cards, and provides relevant configuration information to other drivers or applications that access your PnP cards. By contrast, a PnP configuration utility allows you to view, enter, or change the resource settings of the PnP and legacy cards in your system - the new or changed settings are then used by the PnP configuration driver to configure new PnP cards. For example, the PnP driver for an Ensonique SoundScape board is DWCFGMG.SYS entered into a CONFIG.SYS command line. The corresponding PnP utility for that Ensonique board is SSINIT.EXE which is entered into an AUTOEXEC.BAT command line.

A PnP driver is loaded in the CONFIG.SYS file. For example, the Creative Labs PnP Configuration Manager (for Creative Labs PnP devices) would load the driver CTCM.EXE in a command line such as:

device=c:\ctcmdir\ctcm.exe

where C:\ctcmdir is the directory where you have installed CTCM. This CTCM statement will be placed before all the statements that load other low-level device drivers (such as CTSB16.SYS and SBIDE.SYS) so that your Creative PnP cards will be configured before these device drivers try to use them. For an Ensonique SoundScape sound board, the PnP driver would be installed such as:

device=c:\plugplay\drivers\dos\dwcfgmg.sys

In most cases, an automated installation routine will copy the PnP files to your hard drive, and make any necessary changes to your CONFIG.SYS file. But if you have to install the software manually, make sure to place the driver command line’s for each PnP device after the PnP configuration manager.

A PnP utility is loaded in the AUTOEXEC.BAT file. It is this utility which actually configures and initializes the PnP device. For Creative Labs PnP devices, the utility CTCU is entered in AUTOEXEC.BAT command line(s) such as:

set CTCM=C:\ctcmdir

C:\ctcmdir\CTCU /S /W=C:\windows

where C:\ctcmdir and C:\windows are the directories where your CTCM, CTCU, and Windows 3.x files are installed respectively. For an Ensonique SoundScape sound board, a typical entry would appear similar to:

set sndscape=c:\sndscape

lh c:\sndscape\ssinit /I

Once again, most PnP products will come with an automated installation routine on diskette. But when you are troubleshooting a defective installation or performing a manual installation, the format shown above can help you avoid problems.

When configuring a PnP sound board, you will usually have to deal with a BLASTER variable in the AUTOEXEC.BAT file. For legacy sound cards, the BLASTER variable includes fixed settings for address, interrupt, and DMA information such as:

set BLASTER=A220 I5 D1 T1

With a PnP installation, however, the BLASTER variable is re-defined to "X-out" the interrupt and DMA entries as illustrated below:

set BLASTER=A220 IXX DX T1

The actual values for interrupt and DMA will be entered when the PnP configuration utility runs.

There are a number of "generic" PnP driver/utility sets designed to support a wide range of PnP devices under DOS or Windows 3.1x. One of the most popular is the Intel Configuration Manager (ICM) and ISA Configuration Utility (ICU) - both developed by Intel Corporation. In fact, this software may already be installed on your PC (or bundled with PnP cards). While the idea of generic PnP software is an appealing one, such generic software is not necessarily compatible with all types of PnP boards. When the software and hardware is incompatible, you will see one of the following error messages:

• Failed NVS write,
• Failure to detect PnP BIOS machine
• Failure to assign new configuration to PnP card
• ICM may not be able to configure your PnP card properly

As a general rule, you should use the manufacturer-specific software that accompanies a PnP device rather than generic PnP software.

While manufacturer-specific PnP software will generally provide excellent service, there are some potential limitations to keep in mind. When you use a non-PnP operating system like DOS or Windows 3.1x (and you do not have a PnP BIOS), your PnP card works like a software-configurable card. In such a situation, the PnP driver needs to know which resources have been reserved by all the legacy cards, PnP cards, and system devices in your system before it can allocate conflict-free resources to your new PnP card. Normally, the PnP driver can "see" all the resource settings, but you may need to use the PnP utility to enter the resource settings of all the legacy cards in your PC.

You may still encounter hardware conflicts if the resource settings specified through a PnP utility are incomplete or wrong. If this happens, use the configuration utility to select a different group of resources for the PnP card that caused the conflict. You may need to try a few combinations until you find one that works. This can be tedious, but it is easier than the traditional method of changing DIP switches or jumpers.

DOS PnP software allows you to use PnP devices in the DOS environment. In many cases, DOS support for PnP works adequately, but there are several issues that can arise which you should know how to deal with:

Choosing between the PnP BIOS, PnP software, or PnP OS - There are a number of PC setups that allow you to configure a PnP device based on the PnP BIOS, the PnP driver/utility software, or the PnP operating system. When you are faced with such a choice, it is often better to use the PnP software or operating system rather than the BIOS. Set the BIOS so that it will not configure PnP devices. The reason is that a BIOS does not have any way of knowing how legacy devices are configured, so allowing the BIOS to configure a "mixed" system (with legacy and PnP devices) introduces an excellent chance for hardware conflicts.

NOTE: For "pure" system configurations (containing all PnP devices) you can choose to let the PnP BIOS configure PnP devices.

Upgrading a PnP system to Windows 95 - You may have a system with PnP devices that is running with PnP driver and utility software under DOS or Windows 3.1x. When Windows 95 is installed, it should recognize the PnP device(s) during the hardware detection phase of the installation, then install the proper software for dealing with the device(s) under Windows 95. At the same time, Windows 95 should remark-out the real-mode driver and utility software entries under CONFIG.SYS and AUTOEXEC.BAT. This loss of real-mode drivers can cause a problem when returning to the DOS mode later.

Replacing generic PnP software with manufacturer-specific software - If there is already generic software used to initialize and run your PnP device(s), that software should be disabled before installing manufacturer-specific software. You can do this by placing the REM statement before the generic software’s command lines in CONFIG.SYS and AUTOEXEC.BAT. It is not necessary to remove generic PnP software files from the system.

The system hangs or reboots whenever the driver software loads - The upper memory area of your PnP BIOS machine is probably mapped by EMM386 using the HIGHSCAN option (and thus can get corrupted easily). When it does, CTCM (or other DOS PnP software) will not work properly. Your system may then hang or reboot whenever you load CTCM. To resolve this problem, remove the HIGHSCAN option in the EMM386 statement in the CONFIG.SYS file. For example, change the statement:

device=c:\dir\emm386.exe highscan

to

device=c:\dir\emm386.exe

where C:\dir is the directory in which your EMM386 utility is installed.

Plug-and-Play technology provides technicians and end-users with a powerful configuration tool which takes much of the guesswork and "trial-and-error" out of hardware installations and upgrades. Still, PnP platforms are far from perfect, and managing the mix of PnP and legacy devices in today’s systems takes a bit of care. This part of the chapter provides some tips for working with PnP and legacy devices under Windows 95, then examines a series of PnP troubleshooting procedures.

Ideally, you simply need to install the physical device in the system. When Windows 95 starts, it should recognize the new device automatically, and install the appropriate drivers for it. If Windows 95 cannot locate an appropriate driver already "on-board", it will prompt you to provide a diskette containing the correct driver.

Remember that "legacy" devices are configured manually, and cannot report their configuration to Windows 95 automatically. When installing new legacy hardware in the system, you must run the Add New Hardware wizard to register the device with Windows 95, and add the appropriate driver:

1. In the Control Panel, double-click the Add New Hardware icon.
1. In the Add New Hardware wizard, click Next, then select "Automatically Detect Installed Hardware".
1. Allow Windows 95 to detect the new device, then follow the instructions to configure the driver.

NOTE: There are some cases where the Add New Hardware wizard cannot detect the new device. When this occurs, select "Install Specific Hardware", and you’ll need to specify the new device type, manufacturer, and model - then install the driver.

All devices installed under Windows 95 (both PnP and legacy) are heavily dependent on drivers. Over time, drivers often need to be updated in order to resolve bugs with the driver, streamline the performance of the particular device, or overcome incompatibilities with other devices or drivers. An important part of device management under Windows 95 involves driver updates. In some cases, new drivers are provides on a "maintenance diskette" sent by the manufacturer. In other cases, the new driver is downloaded from the manufacturer’s tech support web site. But in either case, ALL drivers must be properly installed - usually through the Add New Hardware wizard. The following steps outline the process for installing a new driver:

1. In the Control Panel, double-click the Add New Hardware icon.
1. Click Next, click No, and then click Next (do not let the wizard "auto-detect" devices).
1. Click the type of hardware for which you are installing the driver, and then click Next.
1. Click Have Disk.
1. Type the path for the driver you are installing and click OK, or click Browse and locate the driver manually. You must type the path for or locate the Oemsetup.inf file from the manufacturer.
1. In the dialog box listing the .INF file, click OK. Click OK to continue.
1. Click the correct driver and then click OK.
1. Click Finish.

With the popularity of on-line resources such as AOL and the Internet, most current PCs are equipped with a modem. While modem installation is very similar to other device installations, modems offer some peculiar wrinkles which often demand a slightly different installation approach (they are also not always detected with 100% reliability). The steps below outline a modem installation:

1. In the Control Panel, double-click the Modems icon.
1. If this is to be the first modem installed in the computer, the Install New Modem wizard starts automatically. If not, click Add.
1. If you want Windows 95 to "auto-detect" your modem, click Next. If not, click the "Don’t detect my modem..." check box to select it, and then click Next.
1. If you chose to have Windows 95 detect your modem, Windows 95 queries the serial ports on your computer looking for a modem. If Windows 95 detects an incorrect modem, click Change, and select the appropriate manufacturer and model. Click Next, and then continue with step 7.
1. If you chose to select your modem manually, click the appropriate manufacturer and model, and then click Next.
1. Click the appropriate communications port, and then click Next.
1. Click Finish.

Although the newest generation of printers are PnP-compatible and can be identified automatically, most "traditional" printers must be specified under Windows 95 manually. This is accomplished through the Printers icon as specified below:

1. Click the Start button, point to Settings, and then click Printers.
1. Double-click Add Printer, and then click Next.
1. Click Local Printer or Network Printer as appropriate, and then click Next.

NOTE: If you click Network Printer, you are prompted for the network path for the printer. If you do not know the correct path, click Browse, or check with your network administrator. Click either Yes or No as appropriate in the "Do you print from MS-DOS-based programs?" area, and then click Next.

4. Click the appropriate manufacturer and model for your printer, and then click Next.

5. If you chose to install a local printer, click the correct port and then click Next.

6. Type a name for the printer (or accept the default name), and then click either Yes or No in the "Do you want your Windows-based programs to use this printer as the default printer?" area. Click Next.

7. To print a test page, click Yes, then click Finish.

Ordinarily, Windows 95 identifies devices, assigns resources, and loads drivers for all the devices it finds. From time to time (especially during troubleshooting), it may be necessary to "disable" a device. In effect, "disabling" a device prevents Windows 95 from loading drivers or allocating resources associated with the device, but does not "remove" the device from the system. This is a particularly handy trick when checking for resource assignment problems:

1. Click the Start button, point to Settings, and then click Control Panel.
1. Double-click the System icon.
1. On the Device Manager tab, click the device you want, and then click Properties.
1. On the General tab, click the "Original Configuration (Current)" check box to clear it, and then click OK.

You may need to reboot the system in order to free the resources, but the neutralized device should no longer be available.

There will be times (especially during troubleshooting) where it may be necessary to remove a device entirely from the Windows 95 platform in order to free resources otherwise assigned to the device. Normally, Windows 95 should free the resources of a PnP device simply by "disabling" it (see "Disabling a device" above), or when the device is physically removed. But legacy cards may need to be "removed" manually before their assigned resources can be freed. To free resource settings used by disabled hardware:

1. Click Start, Settings, and Control Panel. Click the System icon and select the Device Manager tab.
1. In the hardware list, click the plus sign next to the type of hardware, and then click the device that is disabled.
1. Click Remove, and then click OK.
1. Click the Start button, and then click Shut Down. Click OK. When the message appears saying it is safe to do so, turn off and unplug your computer, and then remove the physical hardware device from inside the computer.

NOTE: PnP device resources are freed automatically when you disable or remove a device. To see if resources are free after the device is disabled but before removing the device, double-click the device in the hardware list in Device Manager, and then click the Resources tab.

Symptom 41-1. Windows 95 fails to recognize the computer as "Plug and Play". This type of problem often occurs with Intel OEM motherboards. Windows 95 does not recognize the computer as a Plug and Play platform - even though you receive a message during startup such as; "Intel PnP BIOS Extensions Installed". Intel has developed some OEM motherboards that are equipped with a Plug and Play BIOS that does not contain the run-time services necessary to configure motherboard devices. An example of such a motherboard is the Intel P5/90. Gateway 2000 (and possibly other OEMs) ship computers with the P5/90 motherboard. You’ll need to upgrade the system BIOS to comply with the Plug and Play BIOS version 1.0a specification or later.

Symptom 41-2. You notice IRQ conflicts with PCI display adapters. When you install a PCI video adapter that is configured to use a particular interrupt (IRQ), Windows 95 may configure it to use another IRQ that is already in use by another device. While PCI devices can share PCI IRQs, Windows 95 does not support sharing PCI IRQs with other non-PCI devices (such as an IDE controller). Use the Device Manager to resolve the conflict by assigning a different IRQ to one of the conflicting devices (usually the new PCI video adapter).

NOTE: This kind of behavior does not occur with ISA or VESA Local Bus VLB display adapters.

Symptom 41-3. The resources for disabled devices are not freed. Even though you disable a device in your computer’s CMOS Setup, Windows 95 re-enables the device and allocates its resources. Windows 95 may also reinstall a device that is removed from Device Manager. This happens because Windows 95 detects Plug and Play devices regardless of the CMOS Setup. To prevent Windows 95 from re-activating disabled hardware, you must disable the hardware in the computer’s CMOS Setup and remove it from the current configuration in Windows 95. This frees the device’s resources for other devices to use:

1. Click the Start button, point to Settings, then click Control Panel.
1. Double-click the System icon.
1. Click the Device Manager tab, then double-click the device you want to disable.
1. Click the General tab, then click the "Original Configuration (Current)" check box to clear it.
1. Click the OK button.
1. Restart Windows 95 when prompted.
1. Immediately start the CMOS Setup routine and disable the device in the CMOS Setup.
1. Save the changes to CMOS, and allow the system to boot normally.

NOTE: When you disable a device in Device Manager, you must restart your computer before you can reassign the device’s resources to another device.

Symptom 41-4. An AST PnP BIOS is not registered as PnP. The AST Plug and Play BIOS is not registered as Plug and Play capable under Windows 95. This is usually because the AST PnP BIOS contains incorrect information in its 16-bit protected-mode entry point. When Windows 95 detects this incorrect code in the AST BIOS it will not recognize the BIOS as Plug and Play capable. You will need to contact AST for a BIOS upgrade.

Symptom 41-5. A PnP ISA adapter is not recognized automatically. If you insert a PnP ISA adapter in a computer whose motherboard does not contain PCI slots, Windows 95 may not recognize the new ISA adapter automatically. The Device Manager may also display a "PCI bus" entry with an exclamation point in a yellow circle, with the status "No Plug and Play ISA bus was found. (Code 29)". This problem is typically caused by a PnP BIOS that is not supported by Windows 95 on computers that have a PCI BIOS, but not a PCI bus. On PCI computers, it is usually the PCI driver that starts the PnP ISA driver. If the PCI driver fails, the ISA driver is not loaded, and therefore PnP ISA adapters are not automatically recognized or configured. To add a PnP adapter so that Windows 95 automatically recognizes it, enable the ISA PnP bus manually:

1. In Control Panel, double-click the Add New Hardware icon, and then click Next.

2. Click No, and then click Next.

3. Click System Devices, and then click Next.

4. Click "ISA Plug And Play Bus", and then click Next.

5. Click Finish.

6. Restart your computer when you are prompted to do so.

You may also want to contact your computer manufacturer to see about obtaining an updated PnP BIOS that is supported by Windows 95.

Symptom 41-6. The computer no longer operates properly after docking or undocking. As an example, the keyboard or mouse may stop working. "Hot docking" and "hot undocking" refer to inserting the computer in a docking station or removing it from the docking station while the computer is running at full power. By contrast, "warm docking" refers to docking or undocking the computer while it is in suspend mode. Laptop or portable computers with a PnP BIOS can be hot or warm docked or undocked. In virtually all cases, the computer does not have a suitable PnP BIOS (this is mandatory for hot or warm docking and undocking). To correct this problem on a permanent basis, you’ll need to upgrade the laptop’s BIOS to a version which supports PnP. In the mean time, you can work around this problem by turning the computer off before you dock or undock it.

Symptom 41-7. Serial PnP devices are not recognized when an adapter is used to connect them. For example, when you use a 9-pin to 25-pin serial adapter with a serial PnP device, the device may not be enumerated by the configuration manager at startup. This is caused by the adapter - some 9-pin to 25-pin serial adapters do not connect the lines that pass the PnP initialization string (including adapters made by Microsoft before the release of Windows 95). Try another (more current) serial adapter. If the problem persists, add the device manually using the Add New Hardware wizard in the Control Panel.

Symptom 41-8. Windows 95 Setup hangs up when detecting SCSI controllers. This often happens with Adaptec SCSI controllers on the first reboot while PnP devices are being detected, and is known to happen when a SCSI hard disk is supported by an Adaptec AHA 2940, Adaptec 2940AU, or Adaptec 2940W controller. You can work around this problem by disabling the SCSI controller and allowing Setup to finish the PnP device detection:

1. Enable PnP SCAM support in the Adaptec SCSI controller BIOS Setup.
1. Disable BIOS Support For Int13 Extension in the Adaptec SCSI controller BIOS Setup.
1. Restart Windows 95, press the <F8> key when you see the "Starting Windows 95" message, and then choose Safe Mode from the Startup menu.
1. In Control Panel, double-click the System icon, click the Performance tab, click File System, and then click the Troubleshooting tab.
1. Enable the following two options; "Disable protect-mode hard disk interrupt handling", and "Disable all 32 bit protect-mode disk drivers".
1. Click OK, and then click OK again.
1. When you are prompted to restart your computer, click Yes to continue with Setup.
1. After Windows 95 is installed, disable the options you enabled in step 5.

Symptom 41-9. After installing an HP OfficeJet 300 printer, you encounter a "Fatal Exception Error" each time you run the Add New Hardware wizard. You’ll typically see Exception Errors 06, 0E, 0C, or 0D. This is because the HP OfficeJet Series 300 Device Manager contends with Windows 95 for control of PnP. The HP installation process sets up a shortcut in the Startup folder that runs "Hpojdman.exe /AUTOPROMPT". This causes Hpojdman.exe to run in the background. Start the Close Program dialog box by pressing <Ctrl>+<Alt>+<Delete>. Click HPOJDMAN in the list of tasks, and then click End Task. Check with HP (www.hp.com) for updated printer software utilities.

Symptom 41-10. The PS/2 mouse is disabled after installing an ISA PnP device. For example, installing a SoundBlaster 16 "value" sound card disables the PS/2 mouse. This problem can occur on computers where the PnP BIOS (rather than Windows 95) assigns resources to ISA PnP devices. The PnP BIOS may assign IRQ 12 to the IDE drive and disable the mouse port. To correct this problem, disable the BIOS PnP support in the computer’s CMOS Setup to allow Windows 95 to configure the hardware instead.

Symptom 41-11. When running the Add New Hardware wizard, it doesn’t detect a device that has been removed in Device manager on a multiple-profile system. This is because removing a PnP device from one profile and leaving it in another causes a flag to be set in the registry to prevent the device from being enumerated on the next startup. This may also cause the Add New Hardware wizard to bypass the device. The flag exists only in the profile in which the device was removed. To prevent this type of problem from occurring, disable the device in Device Manager instead of removing it. To disable a device, click the "Disable In This Hardware Profile" check box for the device in Device Manager. To restore (or re-detect) the device, remove it from all profiles and then run the Add New Hardware wizard.

Symptom 41-12. An extra serial port is displayed in the Device Manager. When you are using Windows 95 OSR 2 or 2.1, you may see an extra communications port in Device Manager. There is an exclamation point in a yellow circle next to the port. If you remove the port, it is re-detected again the next time you restart your computer. The computer’s PnP BIOS is probably reporting (incorrectly) that the COM ports are not using resources - though they were detected during Setup. This is a problem with Windows 95. Check with Microsoft (www.microsoft.com) for any available upgrades or patches.

Symptom 41-13. You cannot setup Windows 95 with a PnP program active. When you try to install Windows 95, you may receive the following error message:

A fatal exception OE has occured at 0028:xxxxxxxx in VxD VMM(06) + xxxxxxxx

Or, you may receive a Vwin32 error message displayed on a blue screen, a registry error message, or a general protection (GP) fault error message. This problem can occur if you have a PnP program active in memory when you try to install Windows 95. To work around this issue, install Windows 95 from a command prompt. Restart the computer. When you see the "Starting Windows 95" message, press the <F8> key, and then choose Command Prompt Only from the Startup Menu. At the command prompt, type;

<drive>:\setup.exe

where <drive> is the drive containing your original Windows 95 Setup disk or CD-ROM.

Symptom 41-14. An IBM ThinkPad doesn’t support PnP under Windows 95. Chances are that the ThinkPad required a BIOS update. The following IBM ThinkPad models are known to need specific BIOS versions:

• ThinkPad 750 family: 750/360/755 System Program Service Diskette version 1.20 or later.
• ThinkPad 755C/Cs and 360/355 family: 750/360/755 System Program Service Diskette version 1.20 or later.
• ThinkPad 755CE/CD, ThinkPad 755CX/CV, ThinkPad 755CDV: 755 System Program Service Diskette version 1.30 or later.
• ThinkPad 701C: 701C System Program Service Diskette version 3H or later.
• ThinkPad 340CSE and 370C: 340 System Program Service Diskette version 1.10 or later.

The following ThinkPad models require APM BIOS 1.1 or later and PnP BIOS 1.0a or later in order for these features to work correctly with Windows 95:

• ThinkPad 755C/Cs
• ThinkPad 360/355 family
• ThinkPad 755CE/CD/CX/CV/CDV
• ThinkPad 340CSE
• ThinkPad 370C
• ThinkPad 701C
• ThinkPad 530CS

The following ThinkPad models require APM BIOS version 1.0 to work correctly with Windows 95. There is no PnP BIOS support for these models:

• ThinkPad 750 family
• ThinkPad 340 monochrome display system
• ThinkPad 230Cs

To obtain an updated BIOS or System Program Service Diskette for an IBM ThinkPad computer, please contact IBM (www.ibm.com).

Symptom 41-15. A PnP pointing device is not detected. When you connect a PnP pointing device (i.e. Microsoft PnP serial mouse, Microsoft EasyBall, or Microsoft IntelliMouse), the new device may not be detected by Windows 95. Running the Add New Hardware wizard does not correct the problem. This is almost always because the registry entries for your previous pointing device were not properly removed from the Registry. This problem is known to occur when your previous pointing device was a Microsoft, Microsoft-compatible, or Logitech mouse. To work around this problem, use the Registry Editor (REGEDIT) to remove the registry entries for your previous pointing device. Remove the following registry keys;

Hkey_Local_Machine\System\CurrentControlSet\Services\Class\Mouse\<nnnn>

where <nnnn> is an incremental 4-digit number starting at 0000. Also remove the following registry keys (if they exist);

Hkey_Local_Machine\Enum\Root\Mouse\<nnnn>

where <nnnn> in an incremental 4-digit number starting at 0000. Remove all registry keys under the following registry key (if they exist);

Hkey_Local_Machine\Enum\Serenum

Remove the following registry key (if it exists);

Hkey_Local_Machine\Software\Logitech\Mouseware

Use the right mouse button to click My Computer, and then click Properties on the menu that appears. Click the Device Manager tab. Click each serial pointing device, and then click Remove. Click OK, then restart Windows 95. When you restart Windows, the attached pointing device will be detected and the appropriate drivers will be installed.

NOTE: Before you edit the Registry, you should first make a backup copy of the registry files (System.dat and User.dat). Both are hidden files in the \Windows folder.

Symptom 41-16. The PnP printer is re-detected every time Windows 95 starts. This occurs even when the printer is already installed. When you start Windows 95, the following message may be displayed:

New Hardware Found

<device>

Windows has found new hardware and is installing the software for it

This problem is known to occur with Hewlett-Packard 4L and Hewlett-Packard DeskJet 660C PnP printers, and is usually caused by damage to the following Registry key:

Hkey_Local_Machine\Enum\Lptenum

Remove the registry key and then restart your computer. When Windows 95 starts, it will detect the printer and install support for it. Once the printer is installed, it will no longer be detected each time you start Windows 95.

NOTE: Before you edit the Registry, you should first make a backup copy of the registry files (System.dat and User.dat). Both are hidden files in the \Windows folder.

Symptom 41-17. After installing Windows 95, none of the APM features were installed. You may also note that there is no "battery meter" for laptops. Some computers and BIOS revisions have known incompatibilities with the APM 1.1 specification. You are probably running Windows 95 on such a computer. As a result, the hardware "suspend" functions of your computer should still function correctly, but you cannot use the Windows 95 APM features. Windows 95 turns off APM support completely on the following computers:

• AMIBIOS 07/08/1994
• AMIBIOS 07/08/94
• any Gateway ColorBook >1.0 w/SystemSoft BIOS
• any Gateway ColorBook with APM 1.0
• AST Ascentia 900N
• Canon Innova 150C
• DECpc LPv+ 1.00
• DECpc LPv+ 1.01
• DECpc LPv+ 1.02
• NCR/AT&T 3150
• NCR/AT&T 3150
• Ultra laptop 486sx33
• Wyse Forte GSV 486/66
• Zenon P5/90

Windows 95 turns off power status polling (so you do not see a battery meter) on the following computers:

• IBM ThinkPad 500
• LexBook
• WinBook

Windows 95 uses APM 1.0 mode on NEC Versa and AT&T Globalyst systems with APM 1.1 BIOS and no Plug and Play BIOS. The following IBM ThinkPad computers support APM 1.1:

• ThinkPad 755C
• ThinkPad 360/355 Family
• ThinkPad 755CE/CD/CX/CV/CDV
• ThinkPad 340CSE
• ThinkPad 370C
• ThinkPad 701C
• ThinkPad 530CS

The following IBM ThinkPad computers work with Windows 95, but only APM BIOS 1.0 is supported:

• ThinkPad 750 family
• ThinkPad 340 (monochrome)
• ThinkPad 230Cs

The ASUS PCI/I P55SP4 motherboard with a SiS 5511/5512/5513 chipset and an Award BIOS has been known to exhibit similar problems (the battery meter may appear on the Taskbar when it should not). This problem should be fixed with PnP BIOS version 0110 (11/21/95) for revision 1.2 and 1.3 motherboards. Revision 1.4 motherboards have this fix using PnP BIOS version 0303 (11/21/95).

Symptom 41-18. The Device Manager reports a "PCI-to-ISA Bridge Conflict". The Device Manager displays a PCI-to-ISA bridge entry with an exclamation point in a yellow circle - indicating that there is a resource conflict. This problem is typically caused by a PnP BIOS that reports both a PCI and an ISA bus, but only an ISA bus is present, so there is no actual conflict. You’ll need to update the PnP BIOS to a version with better detection and reporting capability.

Symptom 41-19. The PnP BIOS is disabled on a laptop or notebook computer. When you install Windows 95 on a dockable notebook computer with a PnP BIOS, you see no "Eject PC" command on the Start menu when the notebook computer is docked in a docking station. Also, no PnP BIOS node is displayed in System Devices under the Device Manager. This problem was known to occur on IBM ThinkPad (360/750/755 series) dockable notebook computers with a PnP BIOS, and occurs because early versions of dockable notebook computers with PnP BIOS are not fully compatible with Windows 95. When a PnP BIOS is disabled in Windows 95, certain features (such as warm docking) no longer work. To make your dockable notebook computer compatible with Windows 95, contact the manufacturer of your notebook computer and obtain the most recent PnP BIOS.

NOTE: In general, a PnP BIOS dated after 7/1/95 is compatible with Windows 95.

Symptom 41-20. The sound device on a DEC HiNote Ultra isn’t working. When you install Windows 95 over an existing Windows for Workgroups 3.1x or Windows 3.1x installation on a DEC HiNote Ultra computer with a PnP BIOS, the sound device no longer works properly. Also, the wrong sound device is installed in Windows 95. This is a PnP BIOS problem - early versions of the DEC HiNote Ultra shipped with a PnP BIOS are not compatible with Windows 95. Contact DEC and obtain the most recent PnP BIOS for the DEC HiNote Ultra.

Symptom 41-21. Device resources are not updated in a "forced" configuration. You’ll notice that an exclamation point appears over a resource icon in Computer properties in Device Manager, or that changes you make to the resources assigned to a PnP device in the computer’s CMOS Setup are not reflected in the "Settings" column in Computer properties under Device Manager. This is because the device is using a "forced" configuration instead of an automatic configuration. To remove a "forced" configuration and allow the PnP device to be fully configurable by the computer’s BIOS and Windows 95, set the device to use automatic settings:

1. Double-click the System icon in Control Panel.
1. Click the Device Manager tab.
1. Double-click the device, and then click the Resources tab.
1. Click the "Use Automatic Settings" check box to select it.
1. Click OK.

NOTE: A "forced" configuration overrides any BIOS or ROM settings (even if Windows 95 knows the device is currently consuming a different set of resources). If you move a device to a different set of resources, you must update the forced configuration manually. When you are diagnosing hardware problems, it is a good idea to look for forced configurations and remove them.

Symptom 41-22. Restarting the computer causes the PC to hang. This often happens when you try to restart your computer using the "Restart the computer" option in the Shut Down Windows dialog box. This problem can occur on computers with a BIOS that expects IRQ 12 to be used by a PS/2-style mouse port, but instead have a software-configurable hardware device (such as a PnP adapter) using IRQ 12. To work around this problem, reserve IRQ 12 in Device Manager, or change the IRQ for the software-configurable device in Device Manager. You may also want to consider upgrading the BIOS in the computer to a later version. To reserve an IRQ with Device Manager:

1. In the Control Panel, double-click the System icon.
1. On the Device Manager tab, double-click Computer.
1. On the Reserve Resources tab, click the Interrupt Request (IRQ) option, and then click Add.
1. In the Value box, click the IRQ you want to reserve.
1. Click OK until you return to Control Panel.

Symptom 41-23. Adding a PCI device to a Dell Dimension causes the system to hang in Windows 95. The BIOS in the Dell computer has probably configured the new PCI device to use IRQ 10, but another legacy device installed in the system is already configured to use IRQ 10. Although Windows 95 is designed to recognize resource conflicts such as this, this particular conflict causes the computer to hang before the Windows 95 Configuration Manager recognizes that the conflict exists. Although the PCI bus is normally a PnP-compatible bus, the BIOS in Dell Dimension computers statically allocates IRQ 10 to a new PCI device - there is no way disable this behavior. To work around this problem, configure the existing legacy device to use an IRQ other than IRQ 10.

Symptom 41-24. You cannot configure disabled devices in the Device Manager. When you’re using a PnP BIOS, you may not be able to configure (through Device Manager) a device that has been disabled in the BIOS - even though the BIOS supports configuring devices for the next time the computer starts. When you click the device in Device Manager and then click Properties, you see a message such as:

The device has been disabled in the hardware. In order to use this device, you must re-enable the hardware. See your hardware documentation for details (Code 29).

This is a problem with Windows 95. You’ll need to enable the device in the BIOS before you try to configure it in Device Manager.

Symptom 41-25. A Toshiba T4900 laptop doesn’t switch from LCD to external monitor. If you place a Toshiba T4900 computer into its docking station while Windows 95 is running (a "warm dock" operation), the display may not switch from the LCD screen to the external monitor. Toshiba's PnP BIOS does not switch the display properly between the LCD screen and an external monitor. For a short-term work around, press the <F5> key to manually toggle the display between the LCD screen and the external monitor. In the mean time, contact Toshiba for a PnP BIOS upgrade.

Symptom 41-26. A third port is detected with a CMD PCI dual-port IDE controller. When using a CMD PCI Dual Port IDE controller (with at least one device on both the primary and secondary port), the Device Manager displays a third port. This "false" third port is displayed with an exclamation point inside a yellow circle. This happens because the PnP BIOS in your computer is erroneously reporting that a third port is present. Windows 95 does not allocate any resources to the third port, and the existence of the third port in Device Manager should not cause any problems. However, if you want to disable the third port, follow these steps:

1. Use the right mouse button to click My Computer, then click Properties on the menu that appears.
1. Click the Device Manager tab.
1. Click the third port, then click Properties. Note that you may need to expand a branch of the hardware tree by double-clicking the branch, or by clicking the plus sign (+) to the left of the branch, before you can click the port.
1. Click the "Original Configuration (Current)" check box to clear it, then click OK.

That’s all for Chapter 41. Be sure to review the glossary and chapter questions on the accompanying CD. If you have access to the Internet, take a look at some of the different PnP resources listed below:

Microsoft’s Plug and Play page: http://www.microsoft.com/hwdev/specs/pnpspecs.htm

Microsoft PnP technology: http://www.microsoft.com/win32dev/base/pnp.htm

Intel's Plug and Play page: http://www.intel.com/IAL/plugplay/index.htm