Comment # 14 on bug 73530 from Alex Deucher

(In reply to comment #9)
> Applying your patch to disable ss to Linux 3.13-rc8 worked. The monitor
> displays now something even with KMS. Thanks!
> 
> It could still be that something else fixed it in Linux 3.13-rc8 which was
> not yet in 3.12.6. I’ll post the logs so you can decide.

Can you test 3.13-rc8 without the ss-patch to confirm what fixed it?