Re: 7970 MAXIMUM KH/S ONLY 600???? *****1000 DOGECOIN REWARD****
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my bios is 015.012.000.004.000346 if you can recommend a particular bios i should try let me know. and i will try flashing it using a bootable usb stick, atiwinflash has worked in the past for me. but maybe i got lucky? cant brick my cards dual bios 
I would try Sapphire.HD7970.3072.120926.rom with the settings and howto I posted before. Let me know what you get, it's something I'm interested in. Also remember you have a switch on the card whitch let you chose between 2 positions for flashing (switching it back permits to 'unbrick' the card because you switch to the standard stock bios).
Considering what has been said about undervolting the 7970s, I would say from my experience that you cannot have high kHs and low consuptions ont those cards (7950 can). I tried to undervolt Sapphire VaporX 7970 (I modified Sapphire.HD7970.3072.120926.rom to 1,081V ) but you instantly get something instable in hashrates > 600kHs.
Thanks..... i tried flashing the bios you mentioned, flashed successfully in DOS. But the card doesn't like the bios and failed to boot. So i flashed the stock bios back. Can you suggest another bios to try?