Hi, we've recently been having some issues overvolting our Sapphire 5850 Xtreme cards, basically having the same issues as some other people in this thread.

I had search around today on the net and found this: http://www.techpowerup.com/forums/showthread.php?p=2308101

Not sure if its right or not, but it looks to be around the right sort of thing you were after? In particular the use of the IC chip used on the card.

Obviously software based overvolting is far more desirable than this risky hardware mod in that thread. Myself and my business partner would be immensely grateful if these issues could be resolved for linux and we'd be willing to throw you a bitcoin or two for your trouble  . We realise its not much, but hopefully others will be able to contribute as well.

Hope this helps, if there's any other information you want us to trawl the web for, we will try and help!