Microsoft KB Archive/74730

= Erratic Keyboard Behavior Using HIMEM.SYS =

Article ID: 74730

Article Last Modified on 11/16/2006

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APPLIES TO


 * Microsoft MS-DOS 5.0 Standard Edition
 * Microsoft MS-DOS 5.0a
 * Microsoft MS-DOS 6.0 Standard Edition
 * Microsoft MS-DOS 6.2 Standard Edition
 * Microsoft MS-DOS 6.21 Standard Edition
 * Microsoft MS-DOS 6.22 Standard Edition

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This article was previously published under Q74730



SUMMARY
You may encounter erratic keyboard behavior when using HIMEM.SYS driver on certain systems. Symptoms may include a variety of problems interpreting the state of the SHIFT, CAPS LOCK, NUM LOCK, ALT, and CTRL keys.

If you encounter this kind of problem, setting the /CPUCLOCK: switch to ON may alleviate the problem. If not, use the HIMEM /machine:xxxx switch to specify an alternative value for the A20 handler. Switches which have been found to be most likely are 11, 12, and 13 (in that order). These switches represent progressively longer delays in the switch state of the A20 line compared to the default handler 1.



MORE INFORMATION
Another workaround is to include the following line in your AUTOEXEC.BAT file.   c:\dos\keyb us,,c:\dos\keyboard.sys KEYB replaces the ROM BIOS INT 09h keyboard interrupt handler with its own routine. This may allow handling of the keyboard in a manner that does not conflict with A20 handling.

Additional query words: 6.22 5.00 5.00a 6.00 6.20 101 key extended enhanced

Keywords: KB74730

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