I'm pretty sure I have discovered the cause of the bug and a fix. The patch is in the upstream bugzilla, and I am currently testing it.
The bug is in xorg-server rather than in the ATI driver. ** Also affects: xorg-server (Ubuntu) Importance: Undecided Status: Unconfirmed ** Changed in: xorg-server (Ubuntu) Status: Unconfirmed => Confirmed -- RandR stops working with MergedFB when the external display is disconnected https://launchpad.net/bugs/37444 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs