EXA for radeon experimental patch

[Soeren Sandmann]

Lars Knoll <lars at trolltech.com> writes:

> Now this is not true for shared memory architectures as the i810, so we would 
> probably need some way to find out how slow framebuffer reads are (and how 
> fast DownloadFromScreen is) and decide the strategy to use based on this 
> information.

Even on shared memory architectures, the "video memory" is
uncached. It is not as slow as real video ram, but slow enough that
doing the compositing in main memory is worthwhile.




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