DOCUMENT:Q104993 20-NOV-1999 [msdos] TITLE :MS-DOS Includes MSD.COM and MSD.EXE PRODUCT :Microsoft Disk Operating System PROD/VER:MS-DOS:6.2,6.21,6.22 OPER/SYS: KEYWORDS: ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft MS-DOS operating system versions 6.2, 6.21, 6.22 ------------------------------------------------------------------------------- SUMMARY ======= MS-DOS includes two files to run Microsoft Diagnostics (MSD): MSD.COM and MSD.EXE. MORE INFORMATION ================ 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 ====================================================================== Keywords : Technology : kbMSDOSSearch kbMSDOS621 kbMSDOS622 kbMSDOS620 Version : MS-DOS: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. Copyright Microsoft Corporation 1999.