3Expansion
H/W .
SETUPCards
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 motherboard also has MIDI enabled, another IRQ will be used, leaving 4 IRQs free.
IMPORTANT: If using PCI cards on shared slots, make sure that the drivers support “Share IRQ” or that the cards do not need IRQ assignments. Conflicts arise between the two PCI groups that will make the system unstable or cards inoperable.
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 |
1 | 2 | Keyboard Controller |
2 | N/A | Programmable Interrupt |
3* | 11 | Communications Port (COM2) |
4* | 12 | Communications Port (COM1) |
5* | 13 | Sound Card (sometimes LPT2) |
6 | 14 | Floppy Disk Controller |
7* | 15 | Printer Port (LPT1) |
8 | 3 | System CMOS/Real Time Clock |
9* | 4 | ACPI Mode when used |
10* | 5 | IRQ Holder for PCI Steering |
11* | 6 | IRQ Holder for PCI Steering |
12* | 7 | PS/2 Compatible Mouse Port |
13 | 8 | Numeric Data Processor |
14* | 9 | Primary IDE Channel |
15* | 10 | Secondary IDE Channel |
*These IRQs are usually available for ISA or PCI devices.
Interrupt Request Table for this Motherboard
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PCI slot 1 | — | shared | — | — |
PCI slot 2 | — | — | shared | — |
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PCI slot 3 | — | — | — | shared |
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PCI slot 4 | shared | — | — | — |
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PCI slot 5 | — | shared | — | — |
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AGP slot | shared | shared | — | — |
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Onboard USB controller | — | — | — | shared |
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Onboard audio/AMR | — | shared | — | — |
26 | ASUS |