SETUP H/W .3
Cards Expansion
3.HARDWARE SETUP
3.7.2Assigning IRQs for Expansion Cards
Some expansion cards need an IRQ to operate. Generally, an IRQ must be exclusively assigned to one use. In a standard design, there are 16 IRQs available but most of them are already in use, leaving 6 IRQs free for expansion cards. If your motherboard has PCI audio onboard, an additional IRQ will be used. If your moth- erboard also has MIDI enabled, another IRQ will be used, leaving 4 IRQs free.
The following table lists the default IRQ assignments for standard PC devices. Use this table when configuring your system and for resolving IRQ conflicts.
Standard Interrupt Assignments
| IRQ | Priority | Standard Function |
0 | 1 | System Timer |
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1 | 2 | Keyboard Controller |
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2 | N/A | Programmable Interrupt |
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3* | 11 | Communications Port (COM2) |
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4* | 12 | Communications Port (COM1) |
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5* | 13 |
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6 | 14 | Floppy Disk Controller |
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7* | 15 | Printer Port (LPT1) |
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8 | 3 | System CMOS/Real Time Clock |
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9* | 4 | ACPI Mode when enabled |
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10* | 5 | IRQ Holder for PCI Steering |
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11* | 6 | IRQ Holder for PCI Steering |
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12* | 7 | PS/2 Compatible Mouse Port |
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13 | 8 | Numeric Data Processor |
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14* | 9 | Primary IDE Channel |
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15* | 10 | Secondary IDE Channel |
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*These IRQs are usually available for ISA or PCI devices.
32 | ASUS P3W User’s Manual |