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ASUS P4T-F User’s Manual
3. HARDWARE SETUP
3. H/W SETUP
Expansion Cards
3.7.2 Assigning 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.
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 enabled
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.
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 will arise
between the two PCI groups that will make the system unstable or cards inoperable.
Interrupt Request Table for this Motherboard
INT-A INT-B INT-C INT-D INT-E INT-F INT-G INT-H
PCI slot 1 —— ———shared ——
PCI slot 2 —————— used —
PCI slot 3 —————— —shared
PCI slot 4 ————used ———
PCI slot 5 ——shared ——— ——
AGP slot used ———————
USB HC0 ———used —— ——
USB HC1 —————— —shared
SMB — shared ———— ——
AC’97 — shared ———— ——