on my 7970 I have 298H/s with 1100/1575, and it works without crash
but i can't improve my Sapphire 280x Tri-X OC to this results, I have only 286H/s in stable. What clocks are you used?
p.s. timings are 1250MHz
Strange

I tried to mod bios, but i did not achieve any increase in performance. Maybe you could share your bios domp of 280x? atm i get 245-260h/s