Ticket #10022 (closed enhancement: fixed)

Opened 11 years ago

Last modified 5 years ago

[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) (diff)

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.



VirtualBox Dos EMM386 failure.png Download (4.2 KB) - added by squib 6 years ago.
Screenshot showing failure

Change History

comment:1 Changed 11 years ago by doug65536

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 Changed 10 years ago by t0re76

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 10 years ago by frank (previous) (diff)

comment:3 Changed 10 years ago by t0re76

same fault running version 4.2.8 r83876 64-bit

comment:4 Changed 7 years ago by aeichner

  • Status changed from new to closed
  • Resolution set to obsolete
  • Description modified (diff)

Please reopen if still relevant with a recent VirtualBox release.

Changed 6 years ago by squib

Screenshot showing failure

comment:5 Changed 6 years ago by squib

  • Status changed from closed to reopened
  • Resolution obsolete deleted

comment:6 Changed 6 years ago by squib

Problem still occurs in v5.1.22 r115126

comment:7 Changed 6 years ago by goodfish

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

comment:8 Changed 5 years ago by bird

  • Status changed from reopened to closed
  • Resolution set to fixed
  • Summary changed from EMM386 does not automatically detect the available UMB regions to [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 Changed 5 years ago by wbpayne

I can confirm this is fixed as of SVN build 120499

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