3.HARDWARE SETUP
3.7.2Assigning 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 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 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 PCI devices.
Expansion Cards
3. H/W SETUP
ASUS | 25 |