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.

Interrupt Request Table for this Motherboard

 

INT-A

INT-B

INT-C

INT-D

PCI slot 1

shared

—

—

—

PCI slot 2

—

used

—

—

 

 

 

 

 

PCI slot 3

—

—

shared

—

 

 

 

 

 

AGP slot

shared

—

—

—

 

 

 

 

 

Onboard USB controller

—

—

—

used

 

 

 

 

 

Onboard audio/SMBus

—

—

shared

—

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 will arise between the two PCI groups that will make the system unstable or cards inop- erable.

Expansion Cards

3. H/W SETUP

ASUS A7V133-M User’s Manual

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