                                                             Last Revised
    AST RESEARCH, INC.        TECHNICAL BULLETIN # 1734          07/01/97

    TITLE:  Adaptec 7800 & Missing Operating System

    ISSUE

       When the user attempts to install NT(version 3.51 or 4.0) on a
       system that is using the Adaptec 7800 controller, under some
       circumstances, Windows NT will complete the first phase of the
       setup, but it will fail when rebooting into Graphical User
       Interface (GUI) mode, displaying the following error message:

                 'Missing Operating System'

       This issue affects all Manhattan D systems.
       This issue was duplicated on system p/n 503223-202.

    BACKGROUND

       This is a known issue with Microsoft Windows NT, and it is dealt
       with on the Microsoft Knowledge Base as Article ID Q143141.

    ACTION

       Prior to installing Windows NT, perform the following two
       actions:

       1. Set the 'Extended Translation BIOS' for hard drives
          >1GB = DISABLED under the Adaptec BIOS Setup.

       2. Create and format a partition on the boot logical
          drive, using MS-DOS or another operating system.

       Upon a successful installation of Windows NT, reset the 'Extended
       Translation BIOS' for hard drives >1GB = ENABLED under the
       Adaptec BIOS Setup.

    NOTES

       N/A

    TAN EPR 600TJ

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