Microsoft KB Archive/89699

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HIMEM.SYS Err Msg: ERROR: Can't Enable A20

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Q89699

3.00 3.00a 3.10 3.11

WINDOWS

kbother kberrmsg

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The information in this article applies to:


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

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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 &quot;Microsoft MS-DOS User's Guide and Reference&quot; for version 5.0.
 * Windows 3.1 HIMEM.SYS Version 3.07

Refer to pages 543-547 of the &quot;Microsoft Windows User's Guide.&quot;
 * 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

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Issue type :

Technology : kbWin3xSearch kbWin300 kbWin300a kbWin310 kbWin311