HIMEM.SYS Err Msg: ERROR: Can't Enable A20 (89699)

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.