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Considering MS-DOG (inside NTVDM) (Users)

posted by Rugxulo Homepage, Usono, 05.08.2011, 23:06

> > Afaik it is not just OS. If you switch a x86 CPU to 64-bit mode, then
> you
> > can't run 16-bit code natively. (because then the "alternate" mode is
> > already pinned to 32-bit)
>
> Yes. AFAIK NTVDM on 32bit windows use virtual x86 mode (that allows 32bit
> supervisor running 16bit sessions) to run most of 16bit code native. But
> when 64bit OS turn CPU to long mode it has no such capability as v86 mode
> (CPU engineers saved some transistors and didn't implement this legacy
> stuff) so you need true PC emulator then. But if I remember well I read
> something that 64bit linux dosemu works and can exec some 16bit code native
> but not sure... It's probably some experimental hack...
> EDIT: from dosemu whatsnew:
> - Added a native 64-bit port for x86-64, which, by default, uses CPU
> emulation
> for V86 mode, and runs DPMI code natively.
> so it seems run only dos 32bit progs native, i'm not sure...3
DOSEMU 32-bit: most stuff works, some doesn't
DOSEMU 64-bit: some stuff works, most doesn't

Quake (DJGPP, 32-bit) works fast as normal, but 16-bit emulation for 64-bit is painfully slow. Either way, neither is perfect (and good luck finding it from your distro), but it's better than nothing. Bugs still exist (as in all emulators), I've accidentally hung the Linux kernel at least twice now (ugh), and I'm not sure you can even use > 64 MB DPMI (default is pitiful 20 MB, eek). But it sure beats the snot out of DOSBox (no LFNs, slow as a 486) for some things (not sound, though).

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