https://bugs.freedesktop.org/show_bug.cgi?id=55692
--- Comment #33 from Serkan Hosca serkan@hosca.com --- (In reply to comment #32)
Other explanation might be that the gdm admin queue a bunch of animation in form of big bo and thus fill up the gart before the first gpu lockup had a chance to be detected.
I'll try lightdm or straight startx from console too