Microsoft KB Archive/35675

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HIMEM.SYS and Windows 2.10 Version Dependencies PSS ID Number: Q35675 Article last modified on 01-05-1989

1.00 1.10 2.00 2.01 2.02 2.03 2.04



HIMEM.SYS, the Microsoft implementation of a XMS (eXtended Memory Specification) device driver, is shipped with MS-DOS Version 4.00 and with Windows Version 2.10. There are different versions of HIMEM.SYS available with different releases of the product, and there are some version-matchings that must be observed. This article will describe this version information for the released versions of HIMEM.SYS.

More Information:

The following table shows the file sizes (in bytes) of the released versions of HIMEM.SYS. Other than noting the version message when HIMEM.SYS is loaded from the CONFIG.SYS, the easiest way to determine which version of this XMS driver you have is to look at the size of the file. (Incidentally, noting the version of HIMEM.SYS will help determine the version of Windows Version 2.10 that you have, which is useful in the discussion below.)

Filename Version Size

HIMEM.SYS 1.00 1613 HIMEM.SYS 1.10 1610 HIMEM.SYS 2.00 4571 HIMEM.SYS 2.01 4777 HIMEM.SYS 2.02 4775 HIMEM.SYS 2.03 5792 HIMEM.SYS 2.04 6223

HIMEM.SYS Version 1.00 was shipped with the first release of Microsoft Windows Version 2.10. This release of Windows and this version of HIMEM.SYS are version locked. This release of HIMEM.SYS is the only release that will work with this version of Windows; conversely, this version of Windows will work only with this version of HIMEM.SYS, not with any other version of HIMEM.SYS (or with any other XMS driver). This version of HIMEM.SYS is not a full XMS device driver; it is only a high memory manager that can be used only by this version of Windows.

HIMEM.SYS Version 1.10 was shipped with later releases of Microsoft Windows Version 2.10. This release of Windows can use this version of HIMEM.SYS, or future versions. In addition, it can use other XMS drivers, in place of HIMEM.SYS Version 1.10. However, HIMEM.SYS Version 1.00 (the previous HIMEM.SYS release) CANNOT be used with this release of Windows. This version of HIMEM.SYS is not a full XMS device driver; it is only a high memory manager. However, this version of Windows uses the XMS interface for accessing the High Memory Area, which allows later versions of HIMEM.SYS to be used in place of Version 1.10.

HIMEM.SYS Versions 2.00, 2.01, 2.02, and 2.03 are not in common public release. For this reason, they will not be discussed in this article.

HIMEM.SYS Version 2.04, the version that is included on the XMS Version 2.00 Distribution Disk, is a fuller implementation of the XMS definition than HIMEM.SYS Versions 1.x. The Version 2.00 through 2.04 releases allow access to extended memory, whereas the 1.x releases only allow access to the high memory area. This version of HIMEM.SYS is shipped with later versions of Windows Version 2.10.

In summary, if you have the first release of Windows Version 2.10, which included HIMEM.SYS Version 1.00, you can only use this version of HIMEM.SYS unless you upgrade to a later version of Windows. If you have a later version of Windows, you can upgrade to the latest version of HIMEM.SYS, if you choose.


Copyright Microsoft Corporation 1989.