Comment # 39 on bug 75992 from Alex Deucher

(In reply to comment #38)
> Created attachment 97208 [details] [review] [review]
> try newer mc ucode
> 
> Try this patch in conjunction with the updated mc firmware here:
> http://people.freedesktop.org/~agd5f/BONAIRE_mc.bin

Make sure the new ucode gets used.  You may have to update your initrd, etc.