i found that the sweet spot on my 4850 is 1.32 to the core,good for 865 in all my benchmark games and still runs cool e-nuff for 24/7 use on my as1 for cooling.
as a matter of factly it seems that it does not scale well with volts after 1.35,max clocks at 1.40v only modest increase to 885 from 1.32v 865.
even with temps 27c ilde 45c load