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MPXplay under CWSDPMI (Users)

posted by Rugxulo Homepage, Usono, 17.10.2010, 01:39

> > It is problem on MPXplay side or on CWSDPMI side?
>
> I would guess it is a CWSDPMI bug. Remember, it isn't intended for real
> work.
CWSDPMI r1 shipped with the original Quake (commercial) in 1996, 1.06 (I think 1.09 was latest in GPL srcs circa 1999). It's also included in some ROMs. And it was used by Norton's Ghost (well, "old" version nowadays). So it's for real work. (Okay, so Quake used DJGPP 2.00 beta3 and that had some *nix sbrk default memory management which had issues with later versions due to changes. But that wasn't his fault, id just decided to abandon DOS as quickly as possible, esp. for NT, which didn't fully support DPMI correctly and hence wouldn't run DOS Quake.) It's the standard host used for DJGPPv2 apps (in stub), at least when not on Windows or OS/2.

The problem is, as Japheth says, probably due to undocumented additions. DOS/4G is more than just a plain "standard" DPMI host. CWSDPMI is "only" a 32-bit DPMI host without any undocumented / non-standard "extended" int 21h APIs, and it doesn't support 16-bit clients at all. According to CWS, various Watcom games (Doom, etc.) needed various unofficial hacks and had bugs and didn't consistently do the right thing. By the time he was writing CWSDPMI (in lieu of unfinished / abandoned MWDPMI or GO32 for v1) for DJGPP v2, nobody ever needed or wanted 16-bit DPMI apps, so nobody complained, and he dropped the issue.

The real question is why you would want to use CWSDPMI here (virtual memory?). I'm not saying you're wrong to try, but if it doesn't work, it doesn't work. :-|

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