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Appendix B: Resolving IRQ Conflicts - Windows
98/Me
We estimate that 95% of Echo installations will go without a hitch
⎯
that Plug-and-
Play will properly assign resources to your card without any conflicts. The other
5% of you may experience interrupt problems (mostly caused by non-Plug-and-
Play ISA cards or PCI cards that don’t like to share). These problems can manifest
themselves by causing your new Echo card to not function properly; in some
instances, devices will fail that were previously working just fine.
If you are having problems with your computer after installing a new Echo card (or
if you are unable to successfully install the card at all), please read the sections
below describing what interrupts are, how they are assigned, and how to work
around interrupt conflicts. Hopefully, we’ll be able to help you solve your problem
without too much trouble.
What is an Interrupt?
A computer has two ways of telling when a device, such as an audio card, is ready
to exchange data with a program. One way is to have the computer periodically ask
or “poll” the device to see if it’s ready to transfer new data. Since it is important to
do the transfer as soon as it is ready, the program must poll the card quite often,
which wastes the computer’s resources.
The other method is to have the card “interrupt” the program when it is ready to
transfer data. It does this by sending a signal over one of the many interrupt wires
connected to the slot into which it is plugged. X86 and Pentium PC’s have 16
possible interrupts (0 to 15), five of which are reserved by the motherboard for the
keyboard, system timer, etc.
ISA and PCI Interrupts
There are two types of expansion connectors found on today’s computers. The
older style connectors are called ISA (for Industry Standard Architecture)
connectors. ISA connectors have 11 of the 16 PC interrupts wired to them. Some
ISA cards (also called “legacy” cards) have you select which interrupt is used by
