Hi Robert, Shane,

> Ben Armstrong ("a Program manager on the core virtualization team
> at Microsoft") recommends the following for MS-DOS on
> http://blogs.msdn.com/virtual_pc_guy/archive/2004/10/21/246136.aspx

Note that this is from 2004 so it cannot be about Virtual PC 2007 ;-)

> device=C:\DOS\EMM386.EXE RAM I=B100-B7FF I=C600-C7FF

Re-using part of mono text buffer (B100-B7FF) and part
of a typical VGA BIOS area (C600-C7FF) sounds a bit
desperate if you ask me... Modern EMM386 such as the
JEMM386 from www.japheth.de that you recommended also
auto-detect the size of the VGA BIOS anyway :-).

> I=CC00-CFFF I=E600-EFFF FRAME=d000



This is odd - Shane Baggs suggested quite different options on 11 March:

> I'm running it on Virtual PC 2007 under Windows XP on a laptop with a Pentium 
> M.
> It crashed at first, but it's now solid as a rock with this line in 
> FDCONFIG.SYS:
>> DEVICE=C:\FDOS\BIN\JEMM386\JEMM386.EXE NOEMS X=CC00-CFFF NOINVLPG
> ... NOEMS is optional.

With NOEMS, no page frame is allocated (it could start at D000 or
later, up to E000). This gives you 64 kB more UMB but old EMS 3.2
software will be unhappy. EMS 4.0 compatible software stays happy.

> NOINVLPG was written by Japheth specifically for [Virtual PC]

Note that classic FreeDOS EMM386 is outdated but probably
did not use INVLPG anyway so you need no specifically-made-
for-Virtual-PC option to fix VPC compatibility either ;-).

> The X=CC00-CFFF was arrived at through testing by trial and error.

So Shane suggests to EXCLUDE CC00-CFFF while Ben suggested
to INCLUDE CC00-CFFF (and D000-DFFF and E600-EFFF...) That
gives  me the idea that Ben wants to say that you should
exclude E000-E5FF instead of CC00-CFFF for "Virtual PC of
the year 2004". Can somebody who has Virtual PC 2007 have
a look at memory contents and about the effects of...

X=cc00-cfff
versus
X=e000-e5ff

...on the stability of FreeDOS with EMM386 / JEMM386? Thanks!

I have the following IDEA: Maybe the X=cc00-cfff, while NOT
using the NOEMS option, had an influence on where the EMS
page frame was, pushing it at the "bad area" - and pushing
UMB area away from it. Because EMS is less often used than
UMB, you still get fewer crashes if the bad area is only in
use while EMS is accessed... You can use MEM or Quarterdeck
MFT / Manifest to see where EMS page frame and UMBs are :-).

Shane, could you post some relevant parts of MEM /D and MEM /E
output with and without X=cc00-cfff combined with with/without
NOEMS option along with information which of those 2 * 2 config
possibilities are stable and which are not? Thank you... :-).

Eric


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