On Tue, 24 Sep 2002, Stas Sergeev wrote:
> Doing the reset call from within DOS brings
> everything back in a sane state.
> Just wondering, why this reset is needed so badly?
Just a very rough guess: proper initialization of certain BIOS variables
in the range 0x400-0x4ff (0040:0000-0040:00ff) ? Try to see what changes
during the init.
> Hmm, my point was that having only the VGA regs
> in hands, it is not possible to lock up the entire
> system. Or is it?
some video cards can be completely manipulated using only VGA ports; for
instance on the SiS the extended registers are 0x3c4, al=5 and up IIRC.
You need to unlock those extended registers, but for that you only need
access to 0x3c4 and 0x3c5, i.e. standard VGA ports.
DOSEMU, because it opens those ports in the "fast" mode, does not check
whether your DOS prog or BIOS tries to write "5" to port 3c4 and then
the appropriate unlock byte to port 3c5.
Now I'm not sure about locking up, but there's certainly a lot you can
do to the graphics card.
> But then it would be possible
> to lock also NT, isn't it?
I have no idea what NT does. I don't know how it opens ports ("slow" or
"fast"). Try [EMAIL PROTECTED] - he should have access to the source
code, I don't.
Bart
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