ATLANTA -- If you add peripheral cards such as sound boards and scanner interfaces to your system, sooner or later you're going to be confronted with something called an IRQ conflict.
IRQ stands for Interrupt ReQuest. An interrupt request basically is a peripheral card's yell to get the microprocessor's attention.
Each device you add needs an IRQ channel for its conversation with the computer.
Some devices are supposed to be able to share channels, but if at all possible each should be assigned its own. Virtually any device you add to your system picks a channel without any action from you. Some of the standard ones -- chiefly the printer and serial ports -- are generally set by the computer itself.
If your new device -- let's say a sound board -- is set for the IRQ 7 channel, and the printer has already been assigned that one, then the sound board isn't going to work properly. The frustrating thing is that your computer may not tell you what's wrong, and it certainly won't tell you what to do about it.
This happened to me when I switched my Sound Blaster Pro card into my new Gateway computer. The Sound Blaster's setup program looked for the card on IRQ 7, and reported it wasn't there, so at least I had an idea of what was wrong.
To check the problem and find a clear channel, I turned to a diagnostic program called QAPlus. One of the many things QAPlus does is provide a list of all your computer's IRQ channels, which are in use and which are available.
QAPlus comes in versions for DOS and for Windows. The Windows version, curiously, does not provide the same kind of IRQ report as the DOS version -- it gives no useful idea of what's in use and what's available.
It does include a wealth of diagnostics and information on your Windows setup, and it also includes a disk with a scaled-down version of QAPlus for DOS, which does provide good IRQ information.
Another good diagnostic program for Windows users is WinSleuth Professional from Dariana. Its interrupt information is more useful than that provided by QAPlus for Windows, but not as accurate as that in the DOS versions. It seemed oblivious to the presence of my sound card.
Both programs run about $90 at discount.