MS-DOS 5, 6, and 6.2 Upgrades Provide DMDRVR.BIN & SSTOR.SYS (78448)

The information in this article applies to:
    Microsoft MS-DOS operating system 5.0
    Microsoft MS-DOS operating system 5.0a
    Microsoft MS-DOS operating system 6.0
    Microsoft MS-DOS operating system 6.2
    Microsoft MS-DOS operating system 6.21
    Microsoft MS-DOS operating system 6.22

This article was previously published under Q78448
This information applies to both Microsoft DoubleSpace and Microsoft DriveSpace. For MS-DOS 6.22, use DRVSPACE in place of DBLSPACE for commands and filenames.


Version 5.0 of DMDRVR.BIN and version 6.3.1 of SSTOR.SYS are provided with Microsoft MS-DOS 5, 6, and 6.2 Upgrades.

NOTE: This version of SSTOR.SYS is NOT compatible with DoubleSpace since it was written before DoubleSpace was released with MS-DOS 6.0. SSTOR.SYS version 6.5 is compatible with DoubleSpace and is available at extra cost from Storage Dimensions. To order this driver, contact their sales department at (408) 954-0710, extension 331.


The MS-DOS ability to access hard drives is based on the standard AT ROM BIOS interface maximum of 1024 cylinders. DMDRVR.BIN and SSTOR.SYS have the ability to work around the 1024 cylinder limit. The drivers are provided with the MS-DOS 5 and later Upgrade packages as a convenience, and are designed to replace existing drivers.

If you use Ontrack Disk Manager, instructions on how to update the driver can be found in section 2.4 of the MS-DOS 5.0 README.TXT file. MS-DOS 5.0 is compatible with DMDRVR.BIN versions 4.xx. According to Ontrack Computer Systems, the version 5.0 driver provided with MS-DOS 5.0 is derived from the original DMDRVR.BIN version 4.2.

If you use HARDRIVE.SYS, instructions on how to update the driver to SSTOR.SYS can be found in section 2.5 of the MS-DOS 5.0 README.TXT file. For MS-DOS 6 and 6.2 instructions, refer to "Setup displays the 'Incompatible hard disk or device driver.' screen" on page 188 of the "Microsoft MS-DOS User's Guide" for versions 6.x.

Please note the following:
    If you use these drivers, your hard drive does not necessarily have to have more than 1024 cylinders.
    DMDRVR.BIN and SSTOR.SYS serve the same purpose. DO NOT LOAD both of the drivers simultaneously. If you have an earlier version of DMDRVR.BIN, expand the new DMDRVR.BIN to the same location; if you have HARDRIVE.SYS, expand SSTOR.SYS to the same location.
    It is recommended that you back up the old version of the drivers to a floppy disk before replacing them.
    DMDRVR.BIN and SSTOR.SYS are provided only with the MS-DOS 5, 6, and 6.2 Upgrades, not with the OEM (original equipment manufacturer) versions.
For more information on the MS-DOS cylinder limitation, query on the following words:

1024 cylinder limit workarounds

DMDRVR.BIN/Disk Manager is a product of Ontrack Computer Systems. SSTOR.SYS is a product of Storage Dimensions, Inc.

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

Modification Type: Major Last Reviewed: 5/12/2003
Keywords: KB78448