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

[Stas Sergeev <stssppnn@yahoo.com>]

Hello.

Bart Oldeman wrote:
>> > c000:0003
>> Where does it do that? I have found only
>> init_vga_card(), but that doesn't seem to be
>> the place. Also I searched the +g log for
>> c000:0003 and found nothing... 
>  src/base/bios/bios.S, line 507, F800:4200. 
>  init_vga_card() pushes f800:4200 on the stack as cs:ip, so that is what
>  DOSEMU gets to execute in the next vm86().
Which means that I've found the proper place not
even realising it:)
Now I also tried to nop out the hardcoded call
directly in bios.S - same effect - no graphics
modes, no even any other text modes, terminal
chars here etc. Only the progs that are setting
modes directly via ports are still working.
Doing the reset call from within DOS brings
everything back in a sane state.
Just wondering, why this reset is needed so badly?

>> > Some people reported black screens, or even machines hanging which
>> > happens when the VBIOS init routine is called.
>> Of course, that was me:) But does the problem still
>> exist after 1.1.3.1?
>  Maybe, maybe not?
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? But then it would be possible
to lock also NT, isn't it?

> It wasn't clear to me whether they used terminal mode or not. Probably
> missed something :(
Well, at least the vbios init was not passed, hence
the term chars.

>> list:( That is why, I think, XFree 3.3.6 or 4.1 are not
>> able to set any VESA modes, but not the 4.2, which can!
>  using VBE 3.0?
What advantages of VBE 3 are you suspecting?
Any chances to find this out without looking into an
XFree sources? Oh well, I just have to look there and
find out all the answers myself, but it is a big pain to
download the entire XFree sources...
Btw, I also played with LRMI package. There is a
program to set the VESA modes. It does iopl(3) and
then int10 in vm86(). Locks up as well...