I have a Sapphire 7950 on the 7970 pcb, voltage unlocked and overclocks fairly well. Not sure what I have it set on atm. But of course I bought this card over a year ago so idk how much has changed on it since then. But, I haven't had any issues with it and its still pushing games like a charm. I am patiently waiting for the 9000 series or w/e they decide to name it.
edit** now that I think about it though, I aint 100% sure if its not trixx allowing me to unlock the voltage. Its been forever since I f'd with the card