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dot.gif (841 bytes) IRQ dot.gif (841 bytes) DMA dot.gif (841 bytes) I/O Addresses

The table below contains a summary line for each of the major device types in a typical PC, showing the major resources that they typically use.

The resources listed below are a guideline, and aren't the hard and fast rule for all devices; consult your manual to see the exact resources used by your hardware. The entries in bold represent the default resource usage in a typical PC; entries in regular text are optional resource allocations, or resources used by optional or non-standard devices:

Device Type

Device

IRQs

DMA Channels

I/O Addresses

System

System reserved

0, 2, 8, 13

0, 4

000-0FFh (except 060h and 064h) and 100-12Fh and 20C-20Dh and 270-277h

PCI devices

9, 10, 11, 12

  

(depends on device)

Serial Ports

COM1

4

  

3F8-3FFh

COM2

3

  

2F8-2FFh

COM3

2/9, 4, 5, 7

  

3E8-3EFh

COM4

2/9, 3, 5, 7

  

2E8-2EFh

Parallel Ports

LPT1

7

1, 3 (if ECP)

378-37Fh, 3BC-3BFh

LPT2

5, 7

1, 3 (if ECP)

278-27Fh, 378-37Fh

LPT3

5

1, 3 (if ECP)

278-27Fh

Input Devices

Keyboard controller

1

  

060h and 064h (shared with PS/2 mouse)

PS/2 mouse

12

  

060h and 064h (shared with keyboard)

Joystick port

    

200-207h

Storage

Floppy disk controller

6

2

3F0-3F7h

Primary IDE controller

14

  

1F0-1F7h and 3F6-3F7h

Secondary IDE controller

15, 10

  

170-177h and 376-377h

Tertiary IDE controller

11, 12

  

1E8-1EFh and 3EE-3EFh

Quaternary IDE controller

10, 11

  

168-16Fh and 36E-36Fh

SCSI host adapter

9, 10, 11, 12, 14, 15

1, 3, 5

130-14Fh, 140-15Fh, 220-23Fh, 330-34Fh, 340-35Fh

Tape accelerator card

3, 4, 5, 6, 7

1, 2, 3

360h, 370h, 3E0h, 3F0h

Old PC/XT hard disk controller

5

3

320-327h

Video

VGA video card

11, 12

  

3B0-3BBh and 3C0-3DFh

EGA video card

2/9

  

3C0-3CFh

Modems

Modem

2/9, 3, 4, 5, 7

1, 3 (voice modems)

(uses COM port)

Sound cards

Sound card

3, 4, 5, 7, 9, 10, 11, 12

(1, 3) and
(5, 6, 7)

(220-22Fh, 240-24Fh, 260-26Fh, 280-28Fh) and (300-301h, 330-331h) and 388-38Bh

Networking

Non-NE2000 network card

3, 4, 5, 7, 9, 10, 11, 12, 15

1, 3, 5, 6, 7

240-243h, 260-263h, 280-283h, 2A0-2A3h, 300-303h, 320-323h, 340-343h, 360-363h

NE2000 network card

3, 4, 5, 7, 9, 10, 11, 12, 15

1, 3, 5, 6, 7

240-25Fh, 260-27Fh, 280-29Fh, 2A0-2BFh, 300-31Fh, 320-33Fh, 340-35Fh, 360-37Fh

IRQ

The table below provides summary information about the 16 IRQ levels in a typical PC. 

IRQ

Bus Line?

Priority

Typical Default Use

Other Common Uses

0

no

1

System timer

None

1

no

2

Keyboard controller

None

2

no (rerouted)

n/a

None; cascade for IRQs 8-15. Replaced by IRQ 9

Modems, very old (EGA) video cards, COM3 (third serial port), COM4 (fourth serial port)

3

8/16-bit

11

COM2 (second serial port)

COM4 (fourth serial port), modems, sound cards, network cards, tape accelerator cards

4

8/16-bit

12

COM1 (first serial port)

COM3 (third serial port), modems, sound cards, network cards, tape accelerator cards

5

8/16-bit

13

Sound card

LPT2 (second parallel port), LPT3 (third parallel port), COM3 (third serial port), COM4 (fourth serial port), modems, network cards, tape accelerator cards, hard disk controller on old PC/XT

6

8/16-bit

14

Floppy disk controller

Tape accelerator cards

7

8/16-bit

15

LPT1 (first parallel port)

LPT2 (second parallel port), COM3 (third serial port), COM4 (fourth serial port), modems, sound cards, network cards, tape accelerator cards

8

no

3

Real-time clock

None

9

16-bit only

4

  

Network cards, sound cards, SCSI host adapters, PCI devices, rerouted IRQ2 devices

10

16-bit only

5

  

Network cards, sound cards, SCSI host adapters, secondary IDE channel, quaternary IDE channel, PCI devices

11

16-bit only

6

  

Network cards, sound cards, SCSI host adapters, VGA video cards, tertiary IDE channel, quaternary IDE channel, PCI devices

12

16-bit only

7

PS/2 mouse

Network cards, sound cards, SCSI host adapters, VGA video cards, tertiary IDE channel, PCI devices

13

no

8

Floating Point Unit (FPU / NPU / Math Coprocessor)

None

14

16-bit only

9

Primary IDE channel

SCSI host adapters

15

16-bit only

10

Secondary IDE channel

Network cards, SCSI host adapters

DMA

The table below provides summary information about the 8 DMA channels in a typical PC.

DMA

Bus Line?

Typical Default Use

Other Common Uses

0

no

Memory Refresh

None

1

8/16-bit

Sound card (low DMA)

SCSI host adapters, ECP parallel ports, tape accelerator cards, network cards, voice modems

2

8/16-bit

Floppy disk controller

Tape accelerator cards

3

8/16-bit

None

ECP parallel ports, SCSI host adapters, tape accelerator cards, sound card (low DMA), network cards, voice modems, hard disk controller on old PC/XT

4

no

None; cascade for DMAs 0-3

None

5

16-bit only

Sound card (high DMA)

SCSI host adapters, network cards

6

16-bit only

None

Sound cards (high DMA), network cards

7

16-bit only

None

Sound cards (high DMA), network cards

I/O Addresses

The table below shows the I/O addresses from 000 to 3FFh, along with the devices that typically use them.

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.

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)

  

Source: www.webopedia.com

Last Update: January 10, 2005
Yannis Grammatis