Messages in this thread | | | Date | Wed, 2 Sep 1998 20:25:48 +0200 | From | Vojtech Pavlik <> | Subject | Re: Next round of console patches |
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On Wed, Sep 02, 1998 at 06:56:06PM +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. > ^^^^^^^^ > Could you explain this? My dictionary has'nt conputer-speak translation > for this...
Sort of 'address space which maps to that card' ... I think, though I'm no native english speaker as well, that this really is similar to the optical meaning of aperture.
> Does it really mean the video memory and mmio overlap? Or is this some > larger area (say 16 MB space) for graphics I/O with the framebuffer (say 4 > MB) at the start and 1k MMIO at the end and some unused space inbetween?
Unfortunately for the Mach64s, the MMIO registers really overlap with the memory, and thus the last 1-2 kilobytes of the video ram are not useable.
Vojtech
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