Cards Expansion

.3 SETUP H/W

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.

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 enabled

 

 

 

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 ISA or PCI devices.

Interrupt Request Table for this Motherboard

 

 

INT-A INT-B INT-C INT-D INT-E INT-F

INT-G INT-H

 

PCI slot 1

—

—

—

—

—

used

—

—

PCI slot 2

—

—

—

—

—

—

used

—

AGP slot

used

—

—

—

—

—

—

—

USB HC0

—

—

—

used

—

—

—

—

USB HC1

—

—

—

—

—

—

—

used

SMB

—

shared

—

—

—

—

—

—

AC’97

—

shared

—

—

—

—

—

—

LAN

—

—

—

—

used

—

—

—

 

 

 

 

 

 

 

 

 

 

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 inoperable.

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ASUS P4T-EM User’s Manual