DOCUMENT:Q89699  24-SEP-1999  [win95x]
TITLE   :HIMEM.SYS Err Msg: ERROR: Can't Enable A20
PRODUCT :Microsoft Windows 95.x Retail Product
PROD/VER:WINDOWS:3.0,3.0a,3.1,3.11
OPER/SYS:
KEYWORDS:

======================================================================
3.00 3.00a 3.10 3.11

WINDOWS

kbother kberrmsg

-------------------------------------------------------------------------------
The information in this article applies to:

 - Microsoft Windows versions 3.0, 3.0a, 3.1, 3.11 
-------------------------------------------------------------------------------

SYMPTOMS
========

You may see one of the following error messages when youstart your system:

   ERROR: Can't enable A20!

-or-

   WARNING: The A20 Line Was Already Enabled.

CAUSE
=====

These error messages indicate that HIMEM.SYS is unable to control the A20 gate
and affect the extended-memory handling system in your computer.

The following can cause these errors to occur:

 - You are loading another memory manager or device driver before loading
   HIMEM.SYS, and it is not allowing HIMEM.SYS access to the A20. Try making a
   bootable system floppy, and in the CONFIG.SYS file make sure that HIMEM.SYS
   is the first device loaded.

 - HIMEM.SYS has incorrectly identified the extended-memory handling mechanism
   on your computer. Try specifying an alternate A20 handler by using the /M:
   command line parameter from a bootable system floppy.

    - Windows 3.0 HIMEM.SYS Version 2.60
      Refer to the README.TXT file that is located in your Windows directory.

    - Windows 3.0 with MS-DOS 5.0 HIMEM.SYS Version 2.77
      Refer to the README.TXT file that is located in your DOS directory and to
      page 610-613 of the "Microsoft MS-DOS User's Guide and Reference" for
      version 5.0.

    - Windows 3.1 HIMEM.SYS Version 3.07
      Refer to pages 543-547 of the "Microsoft Windows User's Guide."

    - MS-DOS 6.0 and 6.2 Systems
      Refer to pages 217-220 of the Microsoft MS-DOS User's Guide for version 6.0
      and 6.2.

 - The machine's BIOS uses an extended-memory handling method that is unknown to
   HIMEM.SYS.

    - If the BIOS is shadowing ROM, then contact your hardware vendor and see if
      this option can be disabled to allow HIMEM.SYS to load.

    - If the BIOS is doing any special handling of the A20, then contact your
      hardware vendor and see if this option can be disabled to allow HIMEM.SYS
      to load.

    - In some cases, a BIOS upgrade from the manufacturer may solve the problem.

Additional query words: err msg winboot 3.10 3.00a 6.00 6.20 3.00 3.11 himemver extended memory

======================================================================
Keywords          :  
Technology        : kbWin3xSearch kbZNotKeyword3 kbWin300 kbWin300a kbWin310 kbWin311
Version           : WINDOWS:3.0,3.0a,3.1,3.11

=============================================================================

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.