I hav a Asus direct Cu 6850...currently im running it @ 950 core and 1180 memory...fan is at 60% and temps r around 66 C...
How much oc is needed to get identical performance to a 6870???
Depends on the card; chances are that with out tweaking the voltage you will never get identical performance. The cards are designed such that with out serious overclocking or bios flashing you will never get the same performance. Close but almost never the same or better performance with a "weaker" card.