Comment 64 for bug 565883

Even without Visual Effects, the radeon driver uses acceleration on the card (EXA, composite etc), so some corruption can be seen. This acceleration is not used if fglrx is blocking, or if you are using the vesa driver ("failsafe").

With compiz it will use hw acceleration for the whole screen, that's why you see it all over.

Did you have any corruption with an older version using fglrx? If not, there is probably a bug in the ati radeon driver. If you did not see corruption in older releases with ati radeon, it could be because it did not use much hw acceleration features at the time.