Microsoft Knowledge Base

• Microsoft MS-DOS operating system versions 6.2, 6.22

1. Q. My computer failed the Microsoft Backup compatibility test. What
      is causing this problem and how can I correct it?

   A. One or more of the following conditions may cause your computer
      to fail the Microsoft Backup compatibility test:

      - The floppy disk drive controller card does not support direct
        memory access (DMA).

      - You are using an incompatible third-party virtual device
        driver (VxD) in Windows.

      - A software or hardware compatibility problem exists (for
        example, you are loading APPEND.EXE, POWER.EXE, or other
        incompatible software).

      When loaded in the [386Enh] section of the SYSTEM.INI file, the
      following software VxDs can cause the Microsoft Backup for Windows
      compatibility test to fail:

         MYABU.386
         FASTBACK.386
         VFD.386
         CPBVXD.386
         VIRWT.386
         CMSTAPE.386
         CMSTAPED.386
         CMSDTAPE.386
         ABACKUP.386

      For a complete list of possible failure causes and steps to
      troubleshoot them, order FastTips Technical Library item Q97577,
      titled "Your Computer Fails the Microsoft Backup Compatibility
      Test."

2. Q. When I try to use Microsoft Backup for MS-DOS, I receive the
      message "DMA Buffer Size Too Small." How can I correct this
      problem?

   A. You can correct this problem by increasing the size of the
      direct memory access (DMA) buffer used by EMM386.EXE. To do
      this, use the following steps:

      1. Use an ASCII text editor, such as MS-DOS Editor, to open your
         CONFIG.SYS file.

      2. Locate the EMM386.EXE command line.

      3. At the end of the EMM386.EXE command line, add the parameter
         D=64.

      4. Save the CONFIG.SYS file, then quit the text editor.

      5. Restart your computer.

      For more information about Microsoft Backup for MS-DOS, refer to
      your MS-DOS 6.2 printed documentation.

3. Q. When I try to use Microsoft Backup for Windows, I receive the
      message: "DMA Buffer Size Too Small." How can I correct this
      problem?

   A. You can correct this problem by increasing the size of the DMA
      buffer used by the extended memory manager and then modifying
      your system initialization file (SYSTEM.INI). To do this, use
      the following steps:

      1. Use a text editor such as MS-DOS Editor to open your
         CONFIG.SYS file.

      2. Locate the EMM386.EXE command line.

      3. At the end of the EMM386.EXE command line, add the parameter
         D=64.

      4. Save the CONFIG.SYS file, then quit the text editor.

      5. Use an text editor to open your SYSTEM.INI file, which is
         located in your Windows directory.

      6. Locate the [386Enh] section and add "DMABuffersize=64"
         (without the quotation marks) after the section heading.

      7. Save the changes to the SYSTEM.INI file, then quit the text
         editor.

      8. Quit Windows if you haven't already done so, and restart your
         computer.