Opened 12 years ago

Closed 6 years ago

Last modified 6 years ago

#10022 closed enhancement (fixed)

[FIXED IN SVN] EMM386 does not automatically detect the available UMB regions

Reported by: t6ti00 Owned by:
Component: other Version: VirtualBox 4.1.6
Keywords: Cc:
Guest type: other Host type: Windows

Description (last modified by aeichner)

If MS-DOS virtual machine is created and EMM386.EXE is used, VirtualBox cannot automatically detect available UMB regions, so they are needed to setup manually to the CONFIG.SYS-file, like:


On the contrary, Microsoft Virtual PC 2007 can do this. Command


is enough and UMB regions will be detected.

This is not a big problem for advanced users who are able to do a manual edit and people who are running only small programs on MS-DOS virtual machines may not need it at all. It can be confusing for the others. I do not consider this is a bug, so let's say that this is a feature request.


Attachments (1)

VirtualBox Dos EMM386 failure.png (4.2 KB ) - added by squib 7 years ago.
Screenshot showing failure

Download all attachments as: .zip

Change History (10)

comment:1 by Doug Gale, 12 years ago

Your "solution" (and others I have found in various forums) of turning off EMS is no good when you need to run a program that requires EMS.

EMM386 issues a warning that memory is present in the I/O area (from B8000 thru EFFFF). Virtual Box is supposed to be virtualizing a PC compatible machine, right? Why isn't it emulating the "memory hole" properly? Real machines (generally) don't have read/write memory in that region, and if they do, it is a part of it, not the whole thing.

All of my attempts to use VBox for a legacy DOS app (that requires EMS) have failed.

This isn't just some little feature request, it *is* a major bug. A blocking bug for the primary use of virtualization outside of a datacenter: running legacy apps.

comment:2 by t0re76, 11 years ago

it could be a software regression IMHO running 4.2.6 r82870 64-bit
windows98 second edition setup after 20 seconds I got

  Standard Mode: Fault outside of MS-DOS Extender.
EC=0000 CS=0B17 IP=0B71 AX=8827 BX02B41 CX=0FDF DX=0000
SI=0000 DI=00F8 BP=8674 DS=0B57 ES=0FDF SS=0B57 SP=866E
Last edited 11 years ago by Frank Mehnert (previous) (diff)

comment:3 by t0re76, 11 years ago

same fault running version 4.2.8 r83876 64-bit

comment:4 by aeichner, 8 years ago

Description: modified (diff)
Resolution: obsolete
Status: newclosed

Please reopen if still relevant with a recent VirtualBox release.

by squib, 7 years ago

Screenshot showing failure

comment:5 by squib, 7 years ago

Resolution: obsolete
Status: closedreopened

comment:6 by squib, 7 years ago

Problem still occurs in v5.1.22 r115126

comment:7 by goodfish, 7 years ago

It's really a big bug, please fix it. 3Q!

comment:8 by bird, 6 years ago

Resolution: fixed
Status: reopenedclosed
Summary: EMM386 does not automatically detect the available UMB regions[FIXED IN SVN] EMM386 does not automatically detect the available UMB regions

This should now be fixed in SVN. Will backport to 5.2 and 5.1 if it doesn't upset too many of our tests.

comment:9 by wbpayne, 6 years ago

I can confirm this is fixed as of SVN build 120499

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