Yeah I've noticed that. I can set 950mv in each dpm state and the card will actually use 950mv in windows, but with the same BIOS in Linux it will use stock voltages of around 1150mv. To get around this I've edited the BIOS to just go ahead and use stock voltages for the higher dpm states but added a 287mv negative global offset...but for some reason dpm state 6 is still bugged. If I switch to that state I see the "AvgPwr" show as around 50W (which tells me it is using less than idle voltage) and it will crash. It should be at around 850 - 863mv in that state, just like it does for states 3, 4, 5, etc. but for some reason it doesn't.

It's a real pain in the ass and I haven't ruled that out as a cause for the instability (briefly switching to state 6 for whatever reason). I wish the driver would just do what it's supposed to according to the BIOS but nope. It does what it wants and what it wants is to be a dick.