BTW: Go Sapphire all the way. Solid as a rock at 0.962v and getting 730kh/sec out of it.
Model and cgminer settings please.
Sku is 11197-03
intensity 20
thread concurrency 40960
shaders 2048
gpu-engine 1100
gpu-memclock 1500
powertune 0
Ah, so this is overclocked. Are you also using the --verbose flag to see if you're getting any HW errors on that intensity?
I am getting 730KH on my 7970 using these:
--thread-concurrency 8192 --gpu-engine 1050 --gpu-memclock 1470 --gpu-powertune 10 -I 13 -g 2 -w 256 --lookup-gap 2 --verbose