Microsoft KB Archive/106427

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Knowledge Base

MS-DOS 6.2x ScanDisk Fails to Correct MDBPB Problem

Article ID: 106427

Article Last Modified on 11/22/1999


  • Microsoft MS-DOS 6.2 Standard Edition
  • Microsoft MS-DOS 6.22 Standard Edition

This article was previously published under Q106427


This information applies to both Microsoft DoubleSpace and Microsoft DriveSpace. For MS-DOS 6.22, use DRVSPACE in place of DBLSPACE for commands and filenames.

ScanDisk may repeatedly detect corruption in the Microsoft DoubleSpace BIOS parameter block (MDBPB) and report it has corrected the problem even though it has not.


This problem is caused by a ScanDisk rounding problem that occurs during the calculation of the minimum estimated compression ratio (ECR).


To work around this problem, reset the DoubleSpace compression ratio and then run ScanDisk. For example:

  1. Set the DoubleSpace compression ratio to any fixed value (that is, don't allow DoubleSpace to set it to the default). For example, type dblspace /ratio=2 at the MS-DOS command prompt and then press ENTER. If your compression ratio is already 2:1, set it to 3:1.
  2. Run ScanDisk to correct the MDBPB problem.
  3. Run DoubleSpace to reset the compression ratio. For example, type "dblspace /ratio" (without the quotation marks) at the MS-DOS command prompt and then press ENTER.


Microsoft has confirmed this to be a problem in MS-DOS ScanDisk version 6.2. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

Additional query words: 6.20

Keywords: KB106427