Comment # 3 on bug 73848 from Alex Deucher

(In reply to comment #0)
> With ASUS Radeon R9 270, just after I boot up and GDM is supposed to start,
> my screen goes blank and some GPU faults are reported in dmesg.
> 
> Upgrading to kernel 3.13 solves this issue.

Any chance you could bisect to see what the fix was?