3Expansion

H/W .

SETUPCards

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 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

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ASUS TR-DLS User’s Manual