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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 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.
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