Assigning Irqs For Expansion Cards - Asus P4T-EM User Manual

3. HARDWARE SETUP

3.7.2 Assigning IRQs for Expansion Cards

Some expansion cards need an IRQ to operate. Generally, an IRQ must be exclu-
sively 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.
Standard Interrupt Assignments
IRQ Priority
0
1
2 N/A
3*
4*
5*
6
7*
8
9*
10*
11*
12*
13
14*
15*
*These IRQs are usually available for ISA or PCI devices.
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 —
PCI slot 2 —
AGP slot used
USB HC0 —
USB HC1 —
SMB —
AC'97 —
LAN —
IMPORTANT:
If using PCI cards on shared slots, make sure that the drivers sup-
port "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.
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Standard Function
1 System Timer
2 Keyboard Controller
Programmable Interrupt
11 Communications Port (COM2)
12 Communications Port (COM1)
13 Sound Card (sometimes LPT2)
14 Floppy Disk Controller
15 Printer Port (LPT1)
3 System CMOS/Real Time Clock
4 ACPI Mode when enabled
5 IRQ Holder for PCI Steering
6 IRQ Holder for PCI Steering
7 PS/2 Compatible Mouse Port
8 Numeric Data Processor
9 Primary IDE Channel
10 Secondary IDE Channel
— — —
— — —
— — —
— — used
— — —
shared — —
shared — —
— — —
ASUS P4T-EM User's Manual
— used —
— — used
— — —
— — —
— — —
— — —
— — —
used — —
—
—
—
—
used
—
—
—