  Hi, there. I don't absolutely sure I've got the same issue, but at least, my
problem is very close to one reported here.

System:
00:01.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Sumo
[Radeon HD 6480G]
xorg-server-1.14.2-alt1
xorg-drv-radeon-7.1.0-alt2
Linux 3.9.10-std-def-alt1

I'm asking you to test the following thing, please: try to

modprobe radeon vramlimit=32

On my system it helps, but only a little: the X screen doesn't freeze, just
highly corrupted. And VTs could be switched. The vramlimit=16 option works the
same way, but any other value I've tried -- 64, 128 --- doesn't!

Does it mean something we can use to trace down this bug?