This might be also related to bug #28925, in case the chip id is there but ati does not give the control to radeon driver.
** Bug 34526 has been marked a duplicate of this bug -- Problems with Radeon X550 https://launchpad.net/bugs/28969 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
