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28 ASUS TR-DLS User’s Manual
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 the motherboard has PCI
audio onboard, an additional IRQ will be used. If the motherboard 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.
ISA Interrupt (IRQ) Assignments
ISA INT Priority Standard Function
ISA 00 1 System Timer
ISA 01 2 Keyboard Controller
ISA 02 N/A Programmable Interrupt
ISA 03* 11 Communications Port (COM2)
ISA 04* 12 Communications Port (COM1)
ISA 05* 13 Sound Card (sometimes LPT2)
ISA 06 14 Floppy Disk Controller
ISA 07* 15 Printer Port (LPT1)
ISA 08 3 System CMOS/Real Time Clock
ISA 09* 4 ACPI Mode when used
ISA 10* 5 IRQ Holder for PCI Steering
ISA 11* 6 IRQ Holder for PCI Steering
ISA 12* 7 PS/2 Compatible Mouse Port
ISA 13 8 Numeric Data Processor
ISA 14* 9 Primary IDE Channel
ISA 15* 10 Secondary IDE Channel
*These IRQs are usually available for PCI devices.
PCI Interrupt (IRQ) Assignments
PCI Slot PCI INTA PCI INTB PCI INTC PCI INTD
1 (64-bit) PCI 5 PCI 13 PCI 15 PCI 14
2 (64-bit) PCI 6 PCI 14 PCI 13 PCI 15
3 (32-bit) PCI 0 PCI 9 PCI 12 PCI 11
4 (32-bit) PCI 1 PCI 10 PCI 9 PCI 12
5 (32-bit) PCI 2 PCI 11 PCI 10 PCI 9
6 (32-bit) PCI 3 PCI 12 PCI 11 PCI 10