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Q81710: 1 MB COMPAQ and AT&T Machines Can’t Run HIMEM.SYS

Article: Q81710
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: 12-OCT-1999

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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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SUMMARY
=======

COMPAQ 286, 386, and 486 machines and the AT&T 6300 Plus, 6386 WGS, 6386/20
WGS implement a memory mapping scheme that does not allow for the installation
of HIMEM.SYS if the machine has only 384K of extended memory.

This information applies to all versions of HIMEM.SYS.

COMPAQ and AT&T computers with more than 1 MB of memory installed function
properly with HIMEM.SYS.

MORE INFORMATION
================

A COMPAQ 286, 386, or 486 with 1 megabyte (MB) installed has 640K base memory
and remaps the 384K extended memory to the 0FA0000 address mark (to the 16 MB
mark, not the 1 MB mark). Because the 384K of extended memory is not addressed
contiguously above the 1 MB line, there is no extended memory in HMA
(1024K-1088K). Therefore, MS-DOS has no place to load high. The
AT&T/Olivetti computer functions in a similar manner.

This behavior occurs by design with COMPAQ and AT&T systems. The design
decision was made by these manufacturers long before HIMEM.SYS was created.
HIMEM.SYS relies on the capability of the 80286/80386/80486 processor to address
64K of extended memory at the 1024K line.

Loading HIMEM.SYS may appear to be successful on some machines while failing to
load or causing system hangs on others. The success depends on the particular
model of COMPAQ or AT&T in use. Alternative machine switches on HIMEM.SYS
will not solve the problem.

COMPAQ has its own OEM version of HIMEM.SYS extended memory manager called
HIMEM.EXE, which is included on the utilities disks with the COMPAQ Deskpro
80286, 80386, and 80486 based systems. It allows those systems with extended
memory to access this extended memory using the extend memory specification
(XMS). It also allows MS-DOS programs to use the 64K region of memory located
just above the 1 MB address.

The version of HIMEM.EXE dated 6-14-90 works with Microsoft Windows version 3.0
and is recommended by COMPAQ for use on COMPAQ machines with less than 16 MB of
memory.

For additional information, contact COMPAQ technical support or AT&T.

The products included here are manufactured by vendors independent of Microsoft;
we make no warranty, implied or otherwise, regard these products' performance
and reliability.

Additional query words: 3.00 3.00a 5.00 systempro 3rdparty 3.10 3.11 6.00 6.20 KBHW

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

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