https://bugs.freedesktop.org/show_bug.cgi?id=33348
--- Comment #22 from Alex Deucher agd5f@yahoo.com 2011-06-17 09:41:13 PDT --- Maybe you are having interrupt problems. run: cat /proc/interrupts and see if you see the interrupts increasing for radeon. You might try the following options on the kernel command line in grub: pci=nomsi irqpoll