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

[t6ti00]

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:

DEVICE=C:\WINDOWS\EMM386.EXE RAM ON NOEMS FRAME=NONE I=E000-EFFF I=B000-B7FF

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

DEVICE=C:\WINDOWS\EMM386.EXE NOEMS

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.

Thanks.

[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.

[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

[t0re76]

same fault running version 4.2.8 r83876 64-bit

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.

[squib]

Screenshot showing failure

[squib]

Problem still occurs in v5.1.22 r115126

[goodfish]

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

[bird]

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.

[wbpayne]

I can confirm this is fixed as of SVN build 120499