https://bugs.freedesktop.org/show_bug.cgi?id=38022
--- Comment #14 from Michel Dänzer michel@daenzer.net 2011-10-17 08:41:37 PDT --- (In reply to comment #13)
The symptoms are essentially the same as Harald described, although on a radeon 9600xt, [...]
That's probably a different issue from this one (which really seems Cayman specific) then. If you can still reproduce the problem with radeon.agpmode=-1, please file your own bug if there isn't one for your card (generation) yet.