### Interrupt Request Line (IRQ) Requirements

An IRQ will be assigned by the PCI BIOS. It should be noted that not all device drivers require an IRQ.

It is important to keep in mind that some older ISA products may have interrupts set by switches or jumpers which may go undetected by the PCI BIOS.

If you are having difficulties with your installation, be sure to verify that your Digi PCI adapter has not been assigned an IRQ that is already being used by another adapter.

The most common sources of contention for IRQs are:

IRQ3: Used by standard serial ports COM2 and COM4, if present.

IRQ5: Used by secondary parallel printer port, if present.

IRQ7: Used by primary parallel printer port, if present.

Many different expansion adapters use IRQs. Check the documentation for the adapters installed in your computer to see which, if any, IRQs they may be using.