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ASUS A7V266-C User’s Manual 27
3. HARDWARE SETUP
Expansion Cards
3. H/W SETUP
3.7.2 Assigning IRQs for Expansion Cards
Some expansion cards need an IRQ to operate. Generally, an IRQ must be exclusively
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 motherboard also
has MIDI enabled, another IRQ will be used, leaving 4 IRQs free.
IMPORTANT: If using PCI cards on shared slots, make sure that the drivers support
“Share IRQ” or that the cards do not need IRQ assignments. Conflicts arise between
the two PCI groups that will make the system unstable or cards inoperable.
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 used
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.
Interrupt Request Table for this Motherboard
INT-A INT-B INT-C INT-D
PCI slot 1 ———shared
PCI slot 2 shared ———
PCI slot 3 — shared ——
PCI slot 4 ——used —
PCI slot 5 ———shared
AGP slot shared shared ——
Onboard audio controller — shared ——
Onboard USB controller ———shared
Onboard IDE controller ———shared