I think your card may be too hot, do not trust your sensor completly, set your fan speed to 100% and see if the hashrate increase
as i said in the first post the card isnt getting hot.
People had bad luck using those cards but they are as good as (better than?) others.
What kind of 7970 do you have ? I'm running a rig with 5 Sapphire 7970 VaporX ( 11197-12-40G ) and at first it was a slooooow 550 kHs / card... Bad.
Now I can get 700-710 and its stable as a rock.
The key was :
1 - flash the card bios ( for me Sapphire.HD7970.3072.120926.rom was the right one )
2 - Update system drivers to amd-catalyst-13.12 and amdapp_2-9 (I'm runnig Linux, don't know if it's the case for you).
3 - Those settings are important :
"intensity" : "13",
"thread-concurrency" : "8192",
"gpu-engine" : "1040",
"gpu-memclock" : "1500",
"gpu-powertune" : "0",
"gpu-threads" : "2",
Ask me if you need more informations about flashing the bios, its not an easy part if you have not done that before
thanks for your help!! My card is a sapphire 7970 (stock cooler) exact model is above in another post, Yes i have flashed bios, only a week ago i flashed another card of mine (a 7950) made a noticeable improvement. Ill give it a shot and report back