Determining Inclusion Address Ranges for EMM386 (78560)

The information in this article applies to:
    Microsoft MS-DOS operating system 5.0

This article was previously published under Q78560


This article contains suggestions for determining whether additional addresses may be included for use by EMM386.


EMM386 excludes A000-C7FF and F000-FFFF by default. The monochrome adapter region (B000-B7FF) may be included if you are not using a monochrome adapter. (Note: If you enter MODE MONO at the command prompt, the system will probably lock up.)

Most video adapters use the region from C000-C5FF. You can determine if your video adapter uses this region by using Debug and entering

d c000:0

at the Debug prompt (-), and examining the first three bytes. The first two bytes should have the ROM signature 55 AA. The next byte indicates the length of the ROM in 512 byte pages. If this reads 30, then the ROM ends at C5FF. If it reads 40, the ROM ends at C7FF. In the former case, you can include this region by specifying I=C600-C7FF only if nothing else is using this include region. You can check if this region is empty by entering the following at the Debug prompt:

d C600:0 l 2000

If the region is empty, it will be filled with FFs.

For more information on including the E000-EFFF region, query on the following words in the Microsoft Knowledge Base:

msdos and emm386 and troubleshoot

In addition, you can use MSD or Quarterdeck Manifest to help determine other memory regions to include with EMM386.

The product included here, Quarterdeck Manifest, is manufactured by a vendor independent of Microsoft; we make no warranty, implied or otherwise, regarding this products' performance or reliability.

Modification Type: Major Last Reviewed: 11/21/1999
Keywords: KB78560