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Standard Interrupt Assignments
IRQ Priority Standard function
0 N/A System Timer
1 N/A Keyboard Controller
2 N/A Programmable Interrupt
3 * 8 Communications Port (COM2)
4 * 9 Communications Port (COM1)
5 * 6 Sound Card (sometimes LPT2)
6 * 11 Floppy Disk Controller
7 * 7 Printer Port (LPT1)
8 N/A System CMOS/Real Time Clock
9 * 10 ACPI Mode when enabled
10 * 3 IRQ Holder for PCI Steering
11 * 2 IRQ Holder for PCI Steering
12 * 4 PS/2 Compatible Mouse Port
13 N/A Numeric Data Processor
14 * 5 Primary IDE Channel
15 * 1 Secondary IDE Channel
* These IRQs are usually available for ISA or PCI devices.
2-5-3 Interrupt Request Table For This Motherboard
Interrupt requests are shared as shown in the table below:
INT A INT B INT C INT D
PCI slot 1 Shared
⎯
⎯
⎯
PCI slot 2
⎯
Shared
⎯
⎯
PCI slot 3
⎯
⎯
Shared
⎯
PCI slot 4
⎯
⎯
⎯
Shared
PCI slot 5 Shared
⎯
⎯
⎯
AGP slot Shared
⎯
⎯
⎯
AC97/MC97
⎯
⎯
Shared
⎯
Onboard USB
⎯
⎯
⎯
Shared
Onboard USB 1
⎯
⎯
⎯
Shared
Onboard USB 2
⎯
⎯
⎯
Shared
IMPORTANT! If using PCI cards on shared slots, make sure that the drivers support “Shared
IRQ” or that the cards don’t need IRQ assignments. Conflicts will arise between
the two PCI groups and will make the system unstable or cards inoperable.