Legacy ISA I/O Address Assignments

The following table lists I/O addresses used by legacy ISA devices and therefore considered fixed.

Legacy ISA System I/O

I/O AddressDefault system function
0000 – 000FSlave DMA
0010 – 0018System
0001FSystem
0020 – 0021Master 8259
0040 – 0043, 0048 – 004BPIT #1, PIT #2
0050 – 0052System
0060Keyboard / mouse controller
0061System control port B
0064Keyboard / mouse status
0070 – 0071NMI Enable / real-time clock
0081 – 008BDMA page registers
0090 – 0091System
0092System control port A
0093 – 009FSystem
00A0 – 00A1Slave interrupt controller
00C0 – 00DEMaster DMA controller
00F0 – 00F1Coprocessor busy clear/reset
0170 – 0177Secondary IDE controller
01F0 – 01F7Primary IDE controller
0201Joystick interface
0220 – 022FSound Blaster
0278 – 027ALPT 2 (XT parallel port 3)
02E8 – 02EFAlternate COM (4)
02F8 – 02FFCOM 2
0330 – 0331MPU-401
0376IDE Controller
0378 – 037ALPT 1 (XT parallel port 2)
0388 – 038BFM synthesis
03B0 – 03BBMDA, EGA / VGA
03BC – 03BELPT 3 (XT parallel port 1)
03C0 – 03DFEGA / VGA
03E0 – 03E7PCIC PCMCIA controllers
03E8 – 03EFAlternate COM (3)
03F0 – 03F7FDC
03F8 – 03FFCOM 1
0534 – 0537Windows Sound System-compatible
0CF8 – 0CFBPCI ports