1. Take lid off case
2. Hook up standard atx psu
3. Up the voltage and OC further
4. Put everything back as it was
5. ???
6. Profit!
On a more serious note what do people reckon the max safe 24/7 voltage is for a 5850 (as long as temps are fine). As I posted previously I'm running 875 core with 1.25v, kept getting gfx driver restarts with 1.2v and that clock. I see no point in OCing beyond what you'd use 24/7 so I'm not interested in safe 1 off voltages just for benching.