On 10/04/2011 01:07 AM, Alan Cox wrote: >> Thats fine as long as you don't want to do acceleration or object >> migration between GTT >> and VRAM type memory. Now I expect when you give out this advice you >> > Yes but the VIA doesn't if I recall correctly have any 'VRAM type memory'. > It's all effectively in the GART with the 'stolen' pages preloaded into > the translation tables by the BIOS at vga init time. >
VRAM memory (at least on the older unichromes) is taken from on-board RAM and set up by the BIOS, and from a device programmer's point of view works like a discrete card VRAM, and is *not* part of the GART. On some devices (K8M800) , the VRAM pages could be accessed by the CPU directly at the top of VRAM, which was substantially faster. There is a fully functional unichrome DRM on top of TTM, that together with the 3D driver in mesa's openchrome branch worked like a charm (even outperformed Intel's i965 with identical CPU at the time). Problem was that it was not backwards compatible with via's old drm. It should serve as a good starting point though, if I can remember where I put it.... /Thomas