IRQ Usage

The following table lists the interrupt request lines (IRQs) that the system typically uses and which ones are available for use by add-on devices.

IRQ

Resource

 

 

NMI

 

 

 

0

System Timer

 

 

1

Keyboard

 

 

2

Cascade

 

 

3

Serial port 2 (COM2)

 

 

4

Serial port 1 (COM1)

 

 

5

Secondary Parallel Port (LPT2)

 

 

6

Floppy Controller

 

 

7

Primary Parallel Port (LPT1)

 

 

8

Real Time Clock (RTC)

 

 

9

Cascade Redirect

 

 

10

Available

 

 

11

Available

 

 

12

PS/2 Mouse Port

 

 

13

Math Coprocessor

 

 

14

Primary Hard Disk

 

 

15

Secondary Hard Disk

 

 

Reference Data 99