Below is a list of the most common bus interupt (IRQ)
assignments for PC/XT
bus and PC/AT (ISA, MCA & EISA) bus based systems. They may
be helpful in
trouble-shooting and/or eliminating potential conflicts when
adding devices
to your computer.
Bus Interupt (IRQ) Assignments For PC/AT (ISA, MCA & EISA)
Buses:
IRQ Type Of Bus Slot Standard Function
---- ---------------- -----------------
0 None System Timer
1 None Keyboard Controller
2 None Second IRQ Controller
3 8-Bit COM Port 2 (or COM 4, if installed/enabled)
4 8-Bit COM Port 1 (or COM 3, if installed/enabled)
5 8-Bit Parallel Port (LPT 2, if installed/enabled)
6 8-Bit Floppy Disk Controller
7 8-Bit Parallel Port (LPT 1)
8 None Real-Time Clock
9 8-Bit Available (Redirected IRQ 2)
10 16-Bit Available
11 16-Bit Available
12 16-Bit PS/2 Mouse Port (if installed/enabled)
13 None Math Coprocessor
14 16-Bit Hard Disk Controller
15 16-Bit Available
Bus Interupt (IRQ) Assignments For PC/XT Buses:
IRQ Type Of Bus Slot Standard Function
---- ---------------- -----------------
0 None System Timer
1 None Keyboard Controller
2 8-Bit Available (early Tandy 1000s used as HD controller)
3 8-Bit COM Port 2 (or COM 4, if installed/enabled)
4 8-Bit COM Port 1 (or COM 3, if installed/enabled)
5 8-Bit Hard Disk Controller (early Tandy 1000s used IRQ 2)
6 8-Bit Floppy Disk Controller
7 8-Bit Parallel Port (LPT 1