Appendix D. Interrupt request and direct memory access channel assignments
The following tables list the IRQ and DMA channel assignments.
Table 4. IRQ channel assignments
IRQ | System resource |
|
|
NMI | Critical system error |
|
|
SMI | |
|
|
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 | |
|
|
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.
Table 5. DMA channel assignments
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. 2001 | 67 |
