for jddebug
What is your intesity setting i am using sapphire r9 280x and MSI 7970 lighting and have found that if I go for intesity higher than -i 2 my rigs start going unstable (restarting,hanging etc..) for the 7970 with downvolt to 1069 mV on the GPU core, on the r9 280 x I can do -i 4 and be stable with the downvolt of 980 mV.
7970 downvolt stable -i 2 get 290 to 300 h/s on claymore 12.4
r9 280 downvolt stable -i 4 get 290 to 300 h/s on claymore 12.4
All cards are running asm option
Hope this helps