Re: [Qemu-devel] Problem with DOS application and 286 DOS Extender application

[Jamie Lokier <jamie@shareable.org>]

Gerhard Wiesinger wrote:
> It is a non public, proprietary application which uses the Ergo Computing 
> 286 DOS Extender. I guess some other application which use the same DOS 
> extender have the same problem. So best thing is to find another 
> application which uses the Ergo Computing 286 DOS Extender, too.

The 286 was obsolete 20 years ago, although code depending on it
persisted for some years after.

I'm fairly sure the number of people using (or trying to use) Qemu
with 286-specific code is very small indeed, so unfortunately for a
286 problem, you will need to help reproduce it as much as you can for
it to be fixed.

Note that Qemu doesn't emulate segments properly even for 32-bit x86
code, and 16-bit (286) code depends on that all the more.  That may be
the problem.

Or it may be the "reset using keyboard controller and BIOS" method
used to switch from protected mode to real mode on a 286 is not
implemented properly, or is not supported by the BIOS properly.

Or it may simply be a bug in 16-bit task segment switching or
something like that, which is quite complex and so rarely used that it
might never have been properly tested.

Did you try running the application under Bochs, which has a more
accurate emulation of very old x86 CPUs?

-- Jamie