Appendix D. Interrupt request and direct memory access channel assignments

 

The following tables list the IRQ and DMA channel assignments.

 

 

IRQ

System resource

 

 

NMI

Critical system error

 

 

SMI

System-management interrupt for power management

 

 

0

Timer

 

 

1

Keyboard

 

 

2

Cascade interrupt from slave PIC

 

 

3

COM2 (some models only)

 

 

4

COM1

 

 

5

Available to user

 

 

6

Diskette controller

 

 

7

LPT1

 

 

8

Real-time clock

 

 

9

Video, ACPI

 

 

10

Available to user

 

 

11

Available to user

 

 

12

Mouse port

 

 

13

Math coprocessor

 

 

14

Primary IDE (if present)

 

 

15

Secondary IDE (if present)

 

 

 

Note: The default settings for COM 1 (IRQ 4), COM 2 (IRQ 3), and LPT 1 (IRQ 7)

can be changed to another IRQ.

DMA channel

Data width

System resource

 

 

 

0

8 bits

Open

 

 

 

1

8 bits

Open

 

 

 

2

8 bits

Diskette drive

 

 

 

3

8 bits

Parallel port (for ECP or EPP)

 

 

 

4

 

Reserved (cascade channel)

 

 

 

5

16 bits

Open

 

 

 

6

16 bits

Open

 

 

 

7

16 bits

Open

 

 

 

© Copyright IBM Corp. 2002

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IBM 2289, 6824 manual DMA channel Data width System resource