https://bugs.freedesktop.org/show_bug.cgi?id=84836
--- Comment #7 from Alexander Tsoy alexander@tsoy.me --- (In reply to Alexander Tsoy from comment #2)
(In reply to Michel Dänzer from comment #1)
Seems to work fine on my Cape Verde. What brand and model do you have specifically?
Gigabyte GV-R775OC-2GI.
JFYI: This card was unstable when operating at 850Mhz sclk (same problem on Windows). After flashing VBIOS from GV-R775D3-2GI (same card physically, but with 800MHz sclk) it works fine now. So this looks like a faulty vendor overclock.