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Q89699: HIMEM.SYS Err Msg: ERROR: Can’t Enable A20

Article: Q89699
Product(s): Microsoft Windows 95.x Retail Product
Version(s): WINDOWS:3.0,3.0a,3.1,3.11
Operating System(s): 
Keyword(s): 
Last Modified: 24-SEP-1999

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

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