Microsoft KB Archive/73446

= Microsoft Knowledge Base =

MACH 20, MS-DOS 5.0, Windows 3.0, and Expanded/Extended Memory
Last reviewed: September 16, 1996

Article ID: Q73446

The information in this article applies to:


 * Microsoft MACH 20, version 1.0
 * Microsoft Windows operating system version 3.0
 * Microsoft MS-DOS operating system version 5.0

SUMMARY
Windows version 3.0 may not run in standard mode on a MACH 20 machine after you upgrade the system to MS-DOS version 5.0. Also, applications that run under MS-DOS do not have access to extended memory.

Running Windows in Standard Mode
If you are running Windows 3.0 on a MACH 20 machine (IBM PC, XT, or compatible with a MACH 20 accelerator card) and you upgrade the machine to MS-DOS 5.0, the upgrade will change the configuration files, which in turn may not enable Windows to run in standard mode. For Windows to run in standard mode, you need to modify the CONFIG.SYS file.

If, after upgrading, you reboot the machine without making the modifications to CONFIG.SYS, you may receive error messages. For example, MS-DOS 5.0 may not recognize the old disk caching driver SMARTDRV.SYS, the high density floppy disk support driver M20DRV.SYS or the old DRIVER.SYS, and HIMEM.SYS will not load.

To correct these problems, you need to use MS-DOS 5.0 SMARTDRV.SYS and, if needed, DRIVER.SYS.

Windows, the MACH 20, and MS-DOS Versions 4.01 and Earlier
Microsoft Windows version 3.00 may not work correctly with Microsoft MACH 20 when using MS-DOS version 4.01 or earlier. After installing Windows, two changes to the configuration need to be made for Windows to take full advantage of the MACH 20 and the extended memory on Memory Plus. These changes require two files on the MACH 20 Windows 3.0 Disk, which is available in Application Note WW0340. For information about obtaining this Application Note, query on the following words in the Microsoft Knowledge Base:

ww0340 and appnote The file DOSX.EXE in the Windows SYSTEM subdirectory needs to be replaced with the one on the MACH 20 Windows 3.0 Disk. The file M20EMM.SYS in the MACH20 subdirectory also should be updated with the newer version from the MACH 20 Windows 3.0 Disk. The syntax in the CONFIG.SYS file should then be modified to read

DEVICE=C:\MACH20\M20EMM.SYS /H=, where  is the number of extended memory pages.

NOTE: There should be 32 pages per 512K of available extended memory.

Extended Memory, the MACH 20, and MS-DOS 5.0
The MACH 20 extended/expanded memory driver (M20EMM.SYS size 15216K, or M20EMM.COM size 15248K, both dated June 14, 1990) does not provide extended memory for Microsoft MS-DOS 5.0 or for any MS-DOS application; however, it does provide extended memory for Windows version 3.0.

The original M20EMM.SYS driver was an expanded memory driver only. When Windows 3.0 began to ship, the driver had to be rewritten to provide HIMEM support for Windows, so it became an expanded/extended memory driver. M20EMM.SYS would have to be rewritten for use with MS-DOS 5.0 as well. As it works now, the M20EMM.SYS driver loads correctly in MS-DOS 5.0 and provides HIMEM support for Windows 3.0, but it doesn't provide HIMEM support for applications running under MS-DOS 5.0. MS-DOS 5.0 will only see the expanded memory.