Less Conventional Memory After Installing MS-DOS 6.21 (113602)

The information in this article applies to:
    Microsoft MS-DOS operating system 6.21
    Microsoft MS-DOS operating system 6.22

This article was previously published under Q113602


When you install MS-DOS Upgrade version 6.21 or 6.22 on a system using MS-DOS 6.0 DoubleSpace, you may notice a reduction in free conventional memory. If all the DoubleSpace files are loaded in the upper memory area, you may not experience this reduction in free conventional memory.


If you have DoubleSpace installed and you install MS-DOS Upgrade over MS-DOS 6.0, DBLSPACE.BIN is modified to give you the equivalent of the MS-DOS 6.2 version of DBLSPACE.BIN. This DBLSPACE.BIN file includes the DoubleGuard and AutoMount features and therefore uses approximately 7 kilobytes (K) more memory. Because MS-DOS 6.21 and 6.22 Upgrade Setup cannot update the MS-DOS 6.0 DBLSPACE.SYS to the equivalent of MS-DOS 6.2 DBLSPACE.SYS, the Microsoft Real-Time Compression Interface (MRCI) libraries cannot be loaded into the high memory area (HMA). As a result, you are more likely to encounter a reduction in conventional memory with MS- DOS 6.21 and 6.22 than with MS-DOS 6.2.


You can regain approximately 4K of conventional memory by deactivating the DoubleSpace AutoMount feature. To do so, type dblspace /automount=0 at the MS-DOS command prompt and then press ENTER. If you do this, you lose the ability to automatically mount compressed removable media (such as compressed floppy disks).

If you are using an 80386 or higher computer, you can also run MemMaker to optimize your use of upper memory blocks. Be sure that your CONFIG.SYS file includes a DEVICE=C:\DOS\DBLSPACE.SYS /MOVE line before you run MemMaker.

Modification Type: Major Last Reviewed: 12/2/1999
Keywords: KB113602