Its not the clock, its the voltage. default voltage for most 5870s is 1.175v. 1v is a huge 18% undervolt.
Or are you saying 700 Mhz doesnt work 1.175v?
I have tried to raise the voltage (which doesn't help)...
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Yeah but he doesnt say how far.
Many cards cant be set any voltage but only to some predefined values. If his cards are not stable at 700 stock voltage he should state that and not post results for 700/1v.
Good point.