Further research: when attempting to place the "top" screen in any other position (left, right, or below other displays), it displays the same noise, but the system doesn't hang. Syslog and kern.log are spammed with a new message:
Oct 22 13:08:28 guilmon kernel: [ 1105.381816] radeon 0000:02:00.0: couldn't schedule ib Oct 22 13:08:28 guilmon kernel: [ 1105.381824] [drm:radeon_cs_ib_chunk] *ERROR* Failed to schedule IB ! -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1243311 Title: GPU lockup when using 2 video cards To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/1243311/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
