Re: please explain to me why video/bios shadowing must be disabled to use graphics...

[phrostie <pfrostie@yahoo.com>]

an update i did finally get dosemu working.
i can run EZ cosmos, commander keen 1-3, and battle chess.
commander keen 4 and above still lock up.  i did notice that the startup 
windows are reporting no or low memory.

On Monday 23 September 2002 17:14, Bart Oldeman wrote:
> On Tue, 24 Sep 2002, Stas Sergeev wrote:
> > This problem exists only on some (modern?) cards for VESA
> > modes, but for VGA modes there must be no such problem at
> > all (Bart, do you really have any examples when this is a
> > problem even for VGA? Correct me then, please).
>
> Well VGA only uses standard ports so the only problem is to pass the
> VBIOS initialization in the first place, that is executing the code at
> c000:0003 (or c800:0003, whereever the VBIOS is). On some graphics cards
> this init routine requires additional open ports and maybe even
> accessible MMIO.
>
> Some people reported black screens, or even machines hanging which
> happens when the VBIOS init routine is called.
>
> I'm not sure why this VBIOS init routine is always called if you set
> $_graphics, but at least it gets the video card into a clean state. This
> is esp. important if you use fbdev graphical textmodes on the console
> instead of the standard VGA textmode (80x25).
>
> Maybe by just bypassing the VBIOS init you can avoid this problem; I
> just have never looked into that possibility.
>
> The VBE 2.0 spec defines a protected mode interface - if DOSEMU would
> use that it could ask which ports should be used and opened. However it
> does not currently use that interface, I don't know how to do that and
> am not able to test it anyway (being far away from my desktop where I
> could take some risks).
>
> Bart
>
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-- 
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