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 |