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# Direct Memory Access (DMA) Channels and Descriptions

Article ID: 104418

Article Last Modified on 5/6/2003

APPLIES TO

- Microsoft MS-DOS 2.11 Standard Edition
- Microsoft MS-DOS 3.1
- Microsoft MS-DOS 3.2 Standard Edition
- Microsoft MS-DOS 3.21 Standard Edition
- Microsoft MS-DOS 3.3 Standard Edition
- Microsoft MS-DOS 3.3a
- Microsoft MS-DOS 4.0 Standard Edition
- Microsoft MS-DOS 4.01 Standard Edition
- Microsoft MS-DOS 5.0 Standard Edition
- Microsoft MS-DOS 5.0a
- Microsoft MS-DOS 6.0 Standard Edition
- Microsoft MS-DOS 6.2 Standard Edition
- Microsoft MS-DOS 6.21 Standard Edition
- Microsoft MS-DOS 6.22 Standard Edition

This article was previously published under Q104418

## SUMMARY

A direct memory access (DMA) channel provides high speed data transfer between a peripheral device, such as a disk drive controller, and memory without intervention by the CPU. Listed below are the DMA channels for the IBM PC and XT class machines and the IBM AT and above class machines.

       IBM PC and XT
       -------------

       DMA Channel        Description
       ---------------------------------------------------

       0               Dynamic RAM Refresh
       1               Reserved
       2               Floppy Disk Controller
       3               Hard Disk Controller

       IBM AT and Above
       ----------------

       DMA Channel        Description
       ---------------------------------------------------

       0               Reserved
       1               SDLC Controller
       2               Floppy Disk Controller
       3               Hard Disk Controller
       4               Cascade from DMA channels 0 - 3
       5               Reserved
       6               Reserved
       7               Reserved

## REFERENCES

"The Handbook For Microcomputer Technicians," by Peter N. Bernstock, ISBN 0-89435-424-8
The products included here are manufactured by vendors independent of Microsoft; we make no warranty, implied or otherwise, regarding these products' performance or reliability.

Additional query words: 6.22 2.00 3.0 3.00 3.1 3.10 3.2 3.20 3.21 3.22 3.3 3.3a 3.30 3.30a 4.0 4.0a 4.00 4.00a 4.01 4.01a 5.0 5.00 5.0a 5.00a 6.00 6.20

Keywords: KB104418