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Standard DMA, I/O and IRQ Assignments

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Standard DMA Assignments
DMAFunctionBus slot required
0UnusedYes (16-bit)
1UnusedYes (8-bit)
2Floppy disk controller boardYes (8-bit)
3UnusedYes (8-bit)
4First DMA controller ICNo (motherboard)
5UnusedYes (16-bit)
6UnusedYes (16-bit)
7UnusedYes (16-bit)

Standard I/O Assignments
000h-00Fh8237A-5 DMA Controller IC #1
020h-03Fh8269A Programmable Interrupt Controller IC #1
040h-05Fh8254-2 System Timer IC
060h8042 Keyboard/Mouse Controller IC
061hSystem board I/0 port
064h8042 Keyboard/Mouse Controller IC
070h-07FhRTC port and NMI mask port
080hPOST code port
080h-09Fh74LS612 DMA Page Registers
0A0h-0BFh8237A-5 Programmable Interrupt Controller IC #2
0F0hClear math coprocessor busy
0F1hReset math coprocessor
0F8h-0FFhMath coprocessor ports
1F0h-1F8hHard disk controller ports (Primary IDE)
170h-178hHard disk controller ports (Secondary IDE)
200h-20FhGame control ports
238h-23BhBus mouse adapter ports
23Ch-23FhAlternative bus mouse adapter ports
278h-27FhParallel printer 2 (LPT2)
2B0h-2DFhAlternative EGA ports
2E0h-2E7hGPIB (Adapter 0)
2E8h-2EFhSerial port 4 (COM4)
2F8h-2FFhSerial port 2 (COM2)
360h-363hNetwork card ports (low)
368h-36BhNetwork card ports (high)
378h-37FhParallel printer 1 (LPT1)
380h-38FhSDLC (bisyne 2) ports
3A0h-3AFhBisyne 1 ports
3B0h-3BBhMonochrome display adapter (MDA) ports
3BCh-3BFhParallel printer 3 (LPT3)
3C0h-3CFhEnhanced graphics adapter (EGA) ports
3D0h-3DFhColor graphics adapter (CGA) ports
3E8h-3EFhSerial port 3 (COM3)
3F0h-3F7hFloppy disk controller ports
3F8h-3FFhSerial port 1 (COM1)

Standard IRQ Assignments
IRQFunctionBus slot required
0System timer ICNo (motherboard)
1Keyboard controller ICNo (motherboard)
2Second IRQ controller ICNo (motherboard)
3Serial port 2 (COM2)*Yes (8-bit)
4Serial port 1 (COM1)*Yes (8-bit)
5Parallel port 2 (LPT2)*Yes (8-bit)
6Floppy disk controller board*Yes (8-bit)
7Parallel port 1 (LPT1)*Yes (8-bit)
8Real-time clock (RTC)No (motherboard)
9Unused (redirected to IRQ 2)Yes (8-bit)
10UnusedYes (16-bit)
11UnusedYes (16-bit)
12Motherboard mouse port (PS2)*Yes (16-bit)
13Math coprocessorNo (motherboard)
14Primary IDE Hard disk controller board*Yes (16-bit)
15Secondary IDE Hard disk controller board*Yes (16-bit)

* Please note that most of these devices are now integrated into the motherboard and no longer require slots. tries to supply accurate and up-to-date information but it is possible that this page may contain typographical errors or technical inaccuracies. Any errors will be periodically corrected as they are made known to us. If any such errors are found, we would appreciate if you would report them here.
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