https://bugs.freedesktop.org/show_bug.cgi?id=42878
--- Comment #1 from Alex Deucher agd5f@yahoo.com 2011-11-13 12:24:10 PST --- (In reply to comment #0)
I think it is too much for one vblank period. Maybe setting voltage/core/memory in separate vblank periods fixes this?
That would definitely help.