Assigning Irqs For Expansion Cards - Asus A7N266-C User Manual

3. HARDWARE 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
0
1
2 N/A
3*
4*
5*
6
7*
8
9*
10*
11*
12*
13
14*
15*
*These IRQs are usually available for ISA or PCI devices.
28
Standard Function
1 System Timer
2 Keyboard Controller
Programmable Interrupt
11 Communications Port (COM2)
12 Communications Port (COM1)
13 Sound Card (sometimes LPT2)
14 Floppy Disk Controller
15 Printer Port (LPT1)
3 System CMOS/Real Time Clock
4 ACPI Mode when used
5 IRQ Holder for PCI Steering
6 IRQ Holder for PCI Steering
7 PS/2 Compatible Mouse Port
8 Numeric Data Processor
9 Primary IDE Channel
10 Secondary IDE Channel
ASUS A7N266-C User's Manual