HP a7v133-vm Manuale Utente

3. HARDWARE SETUP

 Expansion Cards

3.7.2 Assigning IRQs for Expansion Cards

Some expansion cards need an IRQ to operate. Generally, an IRQ must be exclu-
sively 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.

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.

PCI slot 1

shared

—

—

—

PCI slot 2

—

shared

—

—

PCI slot 3

—

—

not shared

—

AGP slot

shared

—

—

—

Onboard USB controller

—

—

—

not shared

Onboard audio/SMBus

—

shared

—

IMPORTANT: If using PCI cards on shared slots, make sure that the drivers sup-
port “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.