
Appendix D. Interrupt request and direct memory access channel assignments
| 
 | The following tables list the IRQ and DMA channel assignments. | 
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| IRQ | System resource | 
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| NMI | Critical system error | 
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| SMI | |
| 
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| 0 | Timer | 
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| 1 | Keyboard | 
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| 2 | Cascade interrupt from slave PIC | 
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| 3 | COM2 (some models only) | 
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| 4 | COM1 | 
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| 5 | Available to user | 
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| 6 | Diskette controller | 
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| 7 | LPT1 | 
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| 8 | |
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| 9 | Video, ACPI | 
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| 10 | Available to user | 
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| 11 | Available to user | 
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| 12 | Mouse port | 
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| 13 | Math coprocessor | 
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| 14 | Primary IDE (if present) | 
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| 15 | Secondary IDE (if present) | 
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| 
 | 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 | 
| 
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| 0 | 8 bits | Open | 
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| 1 | 8 bits | Open | 
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| 2 | 8 bits | Diskette drive | 
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| 3 | 8 bits | Parallel port (for ECP or EPP) | 
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| 4 | 
 | Reserved (cascade channel) | 
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| 5 | 16 bits | Open | 
| 
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| 6 | 16 bits | Open | 
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| 7 | 16 bits | Open | 
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| © Copyright IBM Corp. 2002 | 41 | 
