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From:	Rugxulo <rugxulo AT gmail DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	NTVDM fixes
Date:	Thu, 5 Jun 2008 15:59:44 -0700 (PDT)
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Okay, so I've been using Vista Home Premium (and later SP1) for the
past 10 months, and I've discovered that there are some fixes /
tweaks / workarounds for NTVDM limitations:

1). As you probably know, Vista is shipped in lots of computers now by
default (instead of XP), but it has a 32 MB DPMI limit (for whatever
reason, security??). And supposedly, it's now the same kernel as 2k8,
so that may exhibit the same issue (although fixes untested there by
me). You can get around this problem in two ways:

a). upgrade to SP1 and add the following registry setting (dword) with
the amount you want to use (e.g. "128000000"):

HKLM\System\CurrentControlSet\Control\Wow\DpmiLimit

This works fine for me (although it seems to be undocumented, so I had
to ask somebody "in the know" just to discover it). I used REGEDIT
(and HKLM was HK_LOCAL_MACHINE, for me), if that matters.

b). However, T.R. Nicely has reported that his Vista Home Basic (no
SP1) doesn't improve with this setting. I can only guess that they
fixed something in SP1. And since he's on dialup, he's hard-pressed to
waste his time to download SP1 (was a 66 MB lump, for me at least).
But the following unofficial hack works for him too (although it may
make NTVDM slightly less stable after running DPMI apps):

"HXNTVDM (12k), support tool for NTVDM: This is a DPMI TSR which
supplies additional functionality for DPMI applications in NTVDM.
Might be useful for native DOS-extended applications. Source is
included."

http://www.japheth.de/Download/HXNTVDM.zip    (needs JWasm + Win32inc
to reassemble, both available on his site)

In Vista, at least, you have to run CMD as Admin, put HXVDD.DLL in
\WINDOWS\SYSTEM32, then put HXNTVDM.EXE somewhere in your path. Then,
when you want to run a DPMI app that needs > 32 MB, run the TSR first,
and it will translate DPMI memory calls into Win32 API calls, so it
will work. (As mentioned, this is a much much smaller download than
SP1, so if you're stuck on dialup, this is a good alternative, IMO.)
For the record, this TSR/DLL combo was originally meant to improve /
add upon XP's NTVDM, so the fact that it helps Vista is just icing on
the cake.   ;-)

2). Another TSR for XP etc. is EMS Magic 1.1 (no src, though), which
intends to allow you to relocate the page frame in low memory, fakes
XMS 3.0 by calling XMS 2.0, and (in pure DOS) runs in real mode
instead of slower V86.

http://www.phatcode.net/projects.php?id=102

3). Still another TSR/DLL combo is NTOLDAPP, which lets you access the
clipboard from DOS using the same API as was available in Win9x (e.g.
TDE's DJGPP version, Ctrl-Shift will copy selected text to clipboard
just like the Win32 version does). This one includes src (.ASM, .CPP).
(I can only assume this is the latest version since the original
author's page has disappeared):

http://www.phatcode.net/downloads.php?id=188

P.S. Comments / suggestions to these fixes are welcome.

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