https://bugs.freedesktop.org/show_bug.cgi?id=95017

--- Comment #17 from Michel Dänzer michel@daenzer.net --- (In reply to erhard_f from comment #15)

Played around a bit with xorg and kernel options on my G5 and worked out that I can drive the Radeon 9650 at AGP x8 if I disable DRI completely via Option "NoAccel" "true" in /etc/xorg.conf.

I had no GPU-lockups since then

Sure, because you're not actually using the problematic AGP functionality. :)

and xorg is much more responsive despite lacking DRI hardware acceleration (radeon.agpmode=-1 with DRI enabled).

FWIW, the value of the radeon.agpmode parameter shouldn't matter if you disable DRI (which BTW means no GPU hardware acceleration can be used at all).