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SubjectRe: Next round of console patches
On Wed, 2 Sep 1998, Vojtech Pavlik wrote:
> On Wed, Sep 02, 1998 at 08:20:32AM +0200, Gerd Knorr wrote:
> > There is. The VESA BIOS will tell you (a) how much video memory the board
> > has installed and (b) where the linear framebuffer starts. vesafb (well,
> > the real mode boot code) asks the BIOS for these values and uses this for
> > the framebuffer device. And for exactly this area the mtrr entry is added.
> >
> > Assuming legal framebuffer space and MMIO don't overlap, this works fine.
> As far as I know, this assumption is not true at least for Mach64 based VGA
> cards - they map their MMIO over the last kilobyte of video RAM in the
> aperture.

2 KB for Mach64 VT/GT.

It depends:

- The MMIO overlaps with the little endian aperture only. Big endian rules
again :-)
- You can disable the MMIO overlap and enable the secondary MMIO region.
Don't know what the ATI BIOS does.



Geert Uytterhoeven
Wavelets, Linux/{m68k~Amiga,PPC~CHRP}
Department of Computer Science -- Katholieke Universiteit Leuven -- Belgium

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