https://bugs.freedesktop.org/show_bug.cgi?id=76490
--- Comment #33 from Gustavo Lopes mail@geleia.net --- It doesn't help.
I patched 4.0 rc2 to set the maximum to 1100 Mhz (down from 1200). The computer still hanged after roughly one day running xscreensaver. Another time X seems to have crashed first because I was left seeing two kernel error messages quickly alternating (the same one but about two different rings).