Phil Storrs PC Hardware book

The more common I/O address assignments

I/O Address	USE                                                                                        
0000-000f	Slave DMA controller (8237 chip)
0010-001F	System
0020-0021	First Interrupt controller (8259 chip)
0030-0031 	Second interrupt controller
0040-0043	Programable Interval Timer 1 (8254 chip)
0048-004B	Programable Interval Timer 2
0050-006F	System	devices
0070-0071	NMI Enable / Real Time Clock
0080-008B	DMA Page registers 
0090-009F	System devices
00A0-00A1	Slave interrupt controller
00C0-00DE	Master DMA controller
00F0-00FF	System devices
0100-0167	System devices
0168-016F	IDE Interface - Quaternary channel
0170-0177	IDE interface - Secondary channel
01E8-01EF	IDE Interface - Tertiary channel
01F0-01F7	IDE interface - Primary channel
0200-0207	Games Port (joystick port)
0220-022F	Usually used by sound cards, also used by NOVEL NETWARE KEY CARD
0270-0273	Plug and Play hardware
0278-027A	Parallel  Port *
0280-028F	Sometimes used for LCD Display I/O
02B0-02DF	Alternate VGA Video Display Adaptor assignment (secondary address)
02E0-02E7	GPIB 0, data aquisition card 0 (02E1 to 02E3 only)
02E8-02EF	Serial Port - COM 4
02F8-02FF	Serial Port - COM 2
0300-031F	Often used as a default for Network Interface cards (was prototype card)
0320-023F	ST506 and ESDI Hard Disk Drive Interface (mostly used in PX/XT and early PC/AT)
0330-0331	MPU-401 (midi) interface, on Sound Cards 
0360-036F	Sometimes used for Network Interface cards
0376-0377	Another address used by the Secondary IDE Controller (see 0170-0177)
0378-037A	Parallel Port * 
0388-038B	FM (sound) synthesis port on sound cards
03B0-03BB	MDA, EGA and VGA  Video Display Adaptor  (only 03B0 to 03BB used)
03BC-03BF	Parallel Port (originally only fitted to IBM mono display adaptors) *
03C0-03DF	EGA / VGA Video Display Adaptor, (Primary address)
03E0-03E7	PCIC PCMCIA Port Controller
03E8-03EF	Serial Port - COM 3
03F0-03F6	Floppy Disk Drive Interface
03F7-03f7	Another address used by the Primary IDE Controller (see 01F0-01F7)
03F8-03FF	Serial Port - COM 1
0533-0537	Windows sound system (used by many sound cards)

These next assignments are recent additions, and are used by some modern chip-sets used in System Boards.

0678-067F	Used by the Extended Parallel Port at 0278 (more about EPP soon)
0778-077F	Used by the Extended Parallel Port at 0378 (more about EPP soon) 
07BC-07C5	Used by the Extended Parallel Port at 03BC (more about EPP soon)
0CF8-0CFB	PCI  data registers
FF00-FF07	IDE Bus Mastering Registers
FFA0-FFA7	Primary IDE Bus Mastering Registers
FFA8-FFAF	Secondary IDE Bus Mastering Registers

* The three Parallel Port assignments listed in this table are assigned as LPT1 to LPT3 in the following order : 3BC, 378, 278. Usually a PC has only one Parallel Port and the BIOS setup routines assignes the first Parallel Port hardware it finds in the above order, to LPT1. If a second Parallel Port is found it will be assigned LPT2, in the order above.

Back to the PC and its I/O Ports Back to the opening index Book two index

The PCs Parallel ports The PCs Serial (Comms) ports The Games (Joystick) port

Copyright © Phil. Storr, last updated 26th December 1998