Q104993: MS-DOS Includes MSD.COM and MSD.EXE

Article: Q104993
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:6.2,6.21,6.22
Operating System(s): 
Keyword(s): 
Last Modified: 20-NOV-1999

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The information in this article applies to:

- Microsoft MS-DOS operating system versions 6.2, 6.21, 6.22 
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SUMMARY
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MS-DOS includes two files to run Microsoft Diagnostics (MSD): MSD.COM and
MSD.EXE.

MORE INFORMATION
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MSD versions 2.0, 2.0a, and 2.01 do not interact correctly with expanded memory
services (EMS) memory. MSD makes an INT 67h EMS call and passes an incorrect
buffer pointer. The result is corrupted memory when INT 67h writes information
to this invalid buffer.

To work around this problem, MSD.COM loads before MSD.EXE, hooks INT 67h, and
then monitors for the MSD.EXE INT 67h call. MSD.COM patches the buffer pointer
to point to the correct MSD.EXE data segment. This prevents the data
corruption.

MSD.COM is used rather than making the change in MSD.EXE because MSD.COM can be
used with any 2.x version of MSD.EXE. You can protect against memory corruption
simply by placing the MSD.COM file in the directory where MSD.EXE is located.

Microsoft has confirmed this to be a problem in MSD versions 2.0, 2.0a, and 2.01.
This problem was corrected in MSD version 2.1 (provided with Windows for
Workgroups version 3.11).

Additional query words: 6.22 6.20 now

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Keywords          :  
Technology        : kbMSDOSSearch kbMSDOS621 kbMSDOS622 kbMSDOS620
Version           : MS-DOS:6.2,6.21,6.22

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