Ticket #10022 (reopened enhancement)

Opened 6 years ago

Last modified 3 months ago

EMM386 does not automatically detect the available UMB regions

Reported by: t6ti00 Owned by:
Priority: minor 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 8 months ago.
Screenshot showing failure

Change History

comment:1 Changed 6 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 5 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 5 years ago by frank (previous) (diff)

comment:3 Changed 5 years ago by t0re76

same fault running version 4.2.8 r83876 64-bit

comment:4 Changed 17 months 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 8 months ago by squib

Screenshot showing failure

comment:5 Changed 8 months ago by squib

  • Status changed from closed to reopened
  • Resolution obsolete deleted

comment:6 Changed 8 months ago by squib

Problem still occurs in v5.1.22 r115126

comment:7 Changed 3 months ago by goodfish

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

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