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System Resources
The following sections list the available system resources. See the vendor documentation
delivered with an expansion card or a peripheral device for instructions on how to use these
resources.
ISA Bus Interrupt (IRQ) Assignments
IRQ
Assignment
IRQ
Assignment
0
Reserved (timer/counter)
8
Reserved (real-time clock)
1
Reserved (keyboard controller)
9
USB or Windows sound
2
Reserved (interrupt controller)
10
LAN
3
Serial ports COM 2/COM 4
11
SCSI
4
Serial ports COM 1/COM 3
12
PS/2 mouse
5
Sound card or parallel port LPT 2
13
Reserved (math coprocessor)
6
Reserved (floppy drive controller)
14
Primary IDE
7
Parallel port LPT 1
15
Secondary IDE
Direct Memory Access (DMA) Channels
DMA Channel
Data Width
Assignment
0
8b or 16b
Open
1
8b or 16b
Second choice of ECP parallel port
2
8b or 16b
Floppy drive controller
3
8b or 16b
First choice of ECP parallel port
4
NA
DMA controller to cascade channel
5
16b
Open
6
16b
Open
7
16b
Open
Input/Output (I/O) Addresses
I/O Address (hex)
Size
Assignment
0000–000F
16 bytes
DMA controller 1
0020
−
0021
2 bytes
Interrupt controller 1
0040–0043
4 bytes
Timer/counter 1
0048–004B
4 bytes
Timer/counter 2
