Com 226 comp trouble shooting II theory book
Dealing With Hardware Conflicts
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| Dealing With Hardware Conflicts A PC user recently added a CD-ROM and adapter board to their system. The installation went flawlessly using the defaults—a minute job. Several days later, when attempting to backup the system, the user noticed that the parallel port tape backup did not respond although the printer that had been connected to the parallel port was working fine. The user tried booting the system from a clean bootable floppy disk (no CONFIG.SYS or AUTOEXEC.BAT files to eliminate the device drivers, but the problem remained. After a bit of consideration, the user powered down the system, removed the CD-ROM adapter board, and booted the system from a clean bootable floppy disk. Sure enough, the parallel port tape backup started working again. Stories such as this remind technicians that hardware conflicts are not always the monstrous, system-smashing mistakes that they are made out to be. In many cases, conflicts have subtle, non-catastrophic consequences. Because the CD-ROM was the last device to be added, it was the first to be removed. It took about 5 minutes to realize and remove the problem. However, removing the problem is only part of conflict troubleshooting reinstalling the device without a conflict is the real challenge. Ideally, the way to correct a conflict would be to alter the conflicting setting. That’s dynamite in theory, but another thing in real life. The trick is that you need to know what resources are in use and which ones are free. Unfortunately, there are only two ways to find out. On one hand, you can track down the user manual for every board in the system, then inspect each board individually to find the settings, then work accordingly. This will work assuming that you have the documentation, but it is cumbersome and time consuming. As an alternative, you can use a resource testing tool, such as the Discovery Card by AllMicro, Inc. The Discovery Card plugs into a bit ISA slot and uses a series of LEDs to display each IRQ and DMA channel in use. Any LED not illuminated is an available resource. It is then simply a matter of setting your expansion hardware to an IRQ and DMA channel that is not illuminated. Remember that you might have to alter the command line switches of any device drivers. The only resources not illustrated by the Discovery Card are IO addresses, but because most IO ports are reserved for particular functions (as you saw in Tables 10-3 to 10-5), you can typically locate an unused IO port with a minimum of effort. CONFLICT TROUBLESHOOTING WITH WINDOWS 95 One of the biggest problems with conflict troubleshooting is that every conflict situation is a bit different. Variations in PC equipment and available resources often reduce conflict troubleshooting to a hit or miss process. Fortunately, conflict troubleshooting can be accomplished quickly and easily using the tools provided by Windows 95 (namely the Device Manager. This part of the chapter provides a step-by-step process that you can use for conflict resolution under Windows 95. Step 1: Getting started Start the Device Manager in Windows 95: 1 Click the Start button, then click Settings, then select Control panel. |