KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q104418: Direct Memory Access (DMA) Channels and Descriptions

Article: Q104418
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:2.x,3.x,4.x,5.x,6.0,6.2,6.21,6.22
Operating System(s): 
Keyword(s): 
Last Modified: 17-DEC-2000

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft MS-DOS operating system versions 2.11, 3.1, 3.2, 3.21, 3.3, 3.3a, 4.0, 4.01, 5.0, 5.0a, 6.0, 6.2, 6.21, 6.22 
-------------------------------------------------------------------------------

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          :  
Technology        : kbMSDOSSearch kbMSDOS321 kbMSDOS400 kbMSDOS320 kbMSDOS330a kbMSDOS621 kbMSDOS622 kbMSDOS620 kbMSDOS600 kbMSDOS310 kbMSDOS500 kbMSDOS330 kbMSDOS401 kbMSDOS500a kbMSDOS211
Version           : MS-DOS:2.x,3.x,4.x,5.x,6.0,6.2,6.21,6.22

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.