https://bugs.freedesktop.org/show_bug.cgi?id=66963
--- Comment #162 from Anonymous Helper anonymous@dodgeit.com --- I had a similar problem with my HD 5730M. But I'm not sure if it belongs to this bug. For me it's possible to workaround by delaying the boot process manually: e.g. wait ~20 seconds in the GRUB-Menu or pause the bios booting with the key "Break"
Can somebody confirm that?