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28 ASUS CUW User’s Manual
Expansion Cards
3. H/W SETUP
3. HARDWARE SETUP
3.7.2 Assigning IRQs for Expansion Cards
Some expansion cards need an IRQ to operate. Generally, an IRQ must be exclu-
sively assigned to one use. In a standard design, there are 16 IRQs available but
most of them are already in use, leaving 6 IRQs free for expansion cards. If your
motherboard has PCI audio onboard, an additional IRQ will be used. If your moth-
erboard also has MIDI enabled, another IRQ will be used, leaving 4 IRQs free.
The following table lists the default IRQ assignments for standard PC devices. Use
this table when configuring your system and for resolving IRQ conflicts.
Standard Interrupt Assignments
IRQ Priority Standard Function
0 1 System Timer
1 2 Keyboard Controller
2 N/A Programmable Interrupt
3* 11 Communications Port (COM2)
4* 12 Communications Port (COM1)
5* 13 Sound Card (sometimes LPT2)
6 14 Floppy Disk Controller
7* 15 Printer Port (LPT1)
8 3 System CMOS/Real Time Clock
9* 4 ACPI Mode when enabled
10* 5 IRQ Holder for PCI Steering
11* 6 IRQ Holder for PCI Steering
12* 7 PS/2 Compatible Mouse Port
13 8 Numeric Data Processor
14* 9 Primary IDE Channel
15* 10 Secondary IDE Channel
*These IRQs are usually available for ISA or PCI devices.