I originally dismissed DosBox for its game-oriented disclaimers. In
particular, our application needs LAN access, and they explicitly said
that was not well supported.
Our efforts are now going in a different direction - bringing the
application on more modern hardware in real, not emulated DOS and
figuring out why it fails there. This effort was made in the past and
abandoned, perhaps too soon.
On 10/20/2010 10:19 AM, Bryan J Smith wrote:
If it's PharLap286, I want to almost say -- for certain -- it's first-gen, Ring
0 gobbling VCPI.
Again, an additional test is to try it on 32-bit NT (4-6) and its NTVDM. If it
doesn't work (try several), then it's not DPMI compatible and taking issue with
something else holding Ring 0. DPMI really addresses all of the shortcomings of
VCPI, and allows multi-tasking (really task sharing, to a point, long story) in
DOS. As such, real, 32-bit Virtual86/Protected386 operating systems (NT/NTVDM,
Linux/DOSEmu, etc...) can then offer DPMI with the same capabilities.
I also mentioned DOSBox. DOSBox can actually emulate Ring 0, including for some
VCPI programs. According to the status page, it seems to be limited to Origin
games, don't know what extender they used. Could be unrelated to PharLap and
most early, VCPI-based implementations. But it's worth a shot.
DOSBox isn't a full DOS in the traditional sense, but a DOS emulator that
doesn't require DOS itself. DOSEmu is more like a virtualized DPMI environment,
and then you run DOS under it -- like NTVDM in NT/Windows, although Microsoft
bundles the required DOS support (DOS kernel, COMMAND.COM instead of NT's native
P.S. For several years Concurrent (among others) was marketing itself as a
networked/remote terminal, multiuser DOS solution. Understand these solutions
are based on DR-DOS and DPMI-based DPMS, and will also be incompatible with VCPI
if those services load. Only Real86 DOS without anything using DPMI or an
emulated DOS under another OS, with Ring 0 available (emulated) will work, for
most of those early extenders.
----- Original Message ----
From: Steve Cohen<stevecoh1@xxxxxxxxxxx>
Thanks for this information, Bryan. Unfortunately, it, together with
further investigations into our source code base, convinces me that our
application does indeed depend on the VCPI-based early versions of
PharLap (I didn't know where to look previously) and will ultimately
prove to be incompatible with DOSEmu. Some of the PharLap links are
pretty loose and could possibly be converted to work differently, but
some of the third party stuff like Greenleaf Comms is pretty tightly
linked with PharLap286 and I don't think we want to be changing that.
But that's okay, this little walk down "memory lane" (pun intended)
didn't waste too much time and has given me some other ideas besides
rewrite that may ultimately prove more fruitful.
I'd like to thank all you guys here for your support, Viva Open Source.
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