Created attachment 76994 [details]
dmesg output

Minecraft 1.5.1 locks up the GPU when HyperZ is enabled (which seems to be the
default). When it happens, the screen first freezes for a few seconds, then
becomes black for a few seconds, then the backlight turns off as well, and then
everything recovers. A few seconds later this usually happens again. The
easiest way to get out of this loop is to kill minecraft (I used
AltGr+PrintScreen+F).

I've never seen this happen with any of the older versions of minecraft, but
I'm not sure whether I was using the same kernel and driver versions back then.
Minecraft 1.5.1 has a very different engine than any of the previous versions
(it's about 3 times faster as well), so I think that's why it never happened
before.

I don't get any lockups when I run with R600_HYPERZ=0.

The lockups appear to happen more frequently when the window is larger (I
haven't seen it happen with the default size of 854x480, but at 1920x1080 it
happens all the time. It also happens more often when there's more activity in
Minecraft (e.g. redstone updates).

My card is a Radeon HD 5650M. I'm using Arch Linux, everything is up-to-date.
Kernel version 3.8.4, mesa version 9.1.1.