running 16bit code

[Marcus Meissner]

On Tue, May 08, 2012 at 12:06:23PM +0100, David Laight wrote:
> On Tue, May 08, 2012 at 12:03:52PM +0200, Damjan Jovanovic wrote:
> > On Tue, May 8, 2012 at 11:40 AM, David Laight <david at l8s.co.uk> wrote:
> > > Does wine support running of 16bit windows apps?
> > > If so does it rely on the underlying OS having support
> > > for 'virtual 8086 emulation'?
> > >
> > > I'm thinking of removing the VM86 support from NetBSD,
> > > and wine is about the only likely user.
> > >
> > > ? ? ? ?David
> > >
> > > --
> > > David Laight: david at l8s.co.uk
> > >
> > >
> > 
> > 16 bit Windows applications are written and compiled to either use
> > real mode or 16 bit protected mode.
> > Those that use real mode (mostly MS-DOS and Windows 1 and 2
> > applications) need virtual 8086 mode.
> > Those that use protected mode (mostly Windows >= 3.0 applications)
> > don't need virtual 8086 mode.
> 
> Ok, so wine users would be very unlikely to be affected.
> Since most of the 16bit apps post-date windows 3.

Correct.

> > You'd break DOSBOX a lot more than Wine.
> 
> Possibly, although some emulators are probably better bets for DOS.
> 
> > But why do you want to remove
> > this from NetBSD? I thought compatibility with other operating systems
> > was one of its major features?
> 
> Mainly because it isn't used much, and may well contain security holes.
> There are two separate kernel options VM86 (usually enabled) and
> KVM86 (usually disabled).
> Both change some low level code is obscure ways.

for what it is worth...

DOSBOX and DOSEMU can fall back to full emulation today, so vm86 not
strictly required anymore these days. Speed is probably no longer an
issue ;)

Ciao, Marcus