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[ The PC Guide | Systems and Components Reference Guide | Motherboard and System Devices | System Resources | Input / Output (I/O) Addresses ]

I/O Address Summary Map

The table below shows the I/O addresses from 000 to 3FFh, along with the devices that typically use them. This table is slightly different than the ones that show default and optional use of IRQs and DMA channels. There are many different addresses of different sizes, so in order to keep the table a manageable size, it was made somewhat two-dimensional. Each row is 16 bytes and is divided into four columns; the first is for bytes 0 to 3, the second 4 to 7, the third 8 to B and the fourth C to F. So to find address 3BCh, you would look in the fourth column of row "3B0-3BFh".

Items in the table in bold print represent standard devices in a typical PC configuration. Items in regular print represent optional devices or optional locations for addresses of standard devices. Blank spaces are areas that are open. Multiple lines are used to show multiple items that go in the same address space. Where you see two or more items overlapping in the same address space, there is the potential for a resource conflict.

To see I/O address usage organized by device instead of address, see this device resource summary instead:

Addr.

First Quad
(xx0h to xx3h)

Second Quad
(xx4h to xx7h)

Third Quad
(xx8h to xxBh)

Fourth Quad
(xxCh to xxFh)

000-00Fh

DMA controller, channels 0 to 3

010-01Fh

(System use)

020-02Fh

Interrupt controller #1 (020-021h)

(System use)

030-03Fh

(System use)

040-04Fh

System timers

(System use)

050-05Fh

(System use)

060-06Fh

Keyboard & PS/2 mouse (060h), Speaker (061h)

Keyboard & PS/2 mouse (064h)

 

070-07Fh

RTC/CMOS, NMI (070-071h)

(System use)

080-08Fh

DMA page register 0-2 (081-083h)

DMA page register 3 (087h)

DMA page registers 4-6 (089-08Bh)

DMA page register 7 (08Fh)

090-09Fh

(System use)

0A0-0Afh

Interrupt controller #2 (0A0-0A1h)

(System use)

0B0-0BFh

(System use)

0C0-0CFh

DMA controller, channels 4-7 (0C0-0DFh, bytes 1-16)

0D0-0DFh

DMA controller, channels 4-7 (0C0-0DFh, bytes 17-32)

0E0-0Efh

(System use)

0F0-0FFh

Floating point unit (FPU/NPU/Math coprocessor)

100-10Fh

(System use)

110-11Fh

(System use)

120-12Fh

(System use)

130-13Fh

SCSI host adapter, (130-14Fh, bytes 1 to 16)

140-14Fh

SCSI host adapter, (130-14Fh, bytes 17 to 32)

SCSI host adapter, (140-15Fh, bytes 1 to 16)

150-15Fh

SCSI host adapter, (140-15Fh, bytes 17 to 32)

160-16Fh

 

Quaternary IDE controller, master drive

170-17Fh

Secondary IDE controller, master drive

 

180-18Fh

 

190-19Fh

 

1A0-1AFh

 

1B0-1BFh

 

1C0-1CFh

 

1D0-1DFh

 

1E0-1EFh

 

Tertiary IDE controller, master drive

1F0-1FFh

Primary IDE controller, master drive

 

200-20Fh

Joystick port

 

(System use, 20C-20Dh)

210-21Fh

 

220-22Fh

Sound card

SCSI host adapter, (220-23Fh, bytes 1 to 16)

230-23Fh

SCSI host adapter, (220-23Fh, bytes 17 to 32)

240-24Fh

Sound card

Non-NE2000 network card

 

NE2000 network card (240-25Fh, bytes 1 to 16)

250-25Fh

NE2000 network card (240-25Fh, bytes 17 to 32)

260-26Fh

Sound card

Non-NE2000 network card

 

NE2000 network card (260-27Fh, bytes 1 to 16)

270-27Fh

(System use)

Plug and Play system devices

LPT2 (second parallel port) (color systems)

 

LPT3 (third parallel port) (monochrome systems)

NE2000 network card (260-27Fh, bytes 17 to 32)

280-28Fh

Sound card

Non-NE2000 network card

 

NE2000 network card (280-29Fh, bytes 1 to 16)

290-29Fh

NE2000 network card (280-29Fh, bytes 17 to 32)

2A0-2Afh

vvv

Non-NE2000 network card

 

NE2000 network card (2A0-2BFh, bytes 1 to 16)

2B0-2BFh

NE2000 network card (2A0-2BFh, bytes 17 to 32)

2C0-2CFh

 

2D0-2DFh

 

2E0-2Efh

 

COM4 (fourth serial port)

2F0-2FFh

 

COM2 (second serial port)

300-30Fh

Sound card (MIDI port) (300-301h)

 

Non-NE2000 network card

 

NE2000 network card (300-31Fh, bytes 1 to 16)

310-31Fh

NE2000 network card (300-31Fh, bytes 17 to 32)

320-32Fh

Non-NE2000 network card

 

NE2000 network card (320-33Fh, bytes 1 to 16)

Hard disk controller on old PC/XT

 

330-33Fh

Sound card (MIDI port) (330-331h)

 

NE2000 network card (320-33Fh, bytes 17 to 32)

SCSI host adapter, (330-34Fh, bytes 1 to 16)

340-34Fh

SCSI host adapter, (330-34Fh, bytes 17 to 32)

SCSI host adapter, (340-35Fh, bytes 1 to 16)

Non-NE2000 network card

 

NE2000 network card (340-35Fh, bytes 1 to 16)

350-35Fh

SCSI host adapter, (340-35Fh, bytes 17 to 32)

NE2000 network card (340-35Fh, bytes 17 to 32)

360-36Fh

Tape accelerator card (360h)

 

Quaternary IDE controller (slave drive) (36E-36Fh)

Non-NE2000 network card

 

NE2000 network card (360-37Fh, bytes 1 to 16)

370-37Fh

Tape accelerator card (370h)

Secondary IDE controller (slave drive) (376-377h)

LPT1 (first parallel port) (color systems)

 

LPT2 (second parallel port) (monochrome systems)

NE2000 network card (360-37Fh, bytes 17 to 32)

380-38Fh

 

Sound card (FM synthesizer)

 

390-39Fh

 

3A0-3AFh

 

3B0-3BFh

VGA/Monochrome Video

LPT1 (first parallel port) (monochrome systems)

3C0-3CFh

VGA/EGA Video

3D0-3DFh

VGA/CGA Video

3E0-3EFh

Tape accelerator card (3E0h)

 

COM3 (third serial port)

 

Tertiary IDE controller (slave drive) (3EE-3EFh)

3F0-3FFh

Floppy disk controller

COM1 (first serial port)

Tape accelerator card (3F0h)

Primary IDE controller (slave drive) (3F6-3F7h)

 

Next: Logical Devices


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