I recently built a PC with a diamond HD 5850 and I am considering OCing it from GPU clock 760 and memory clock 1050 TO GPU clock 850 and memorcy clock 1200 (5870 stock standards). The thing is I am completely new to overclocking and the only reason I want to is that I cant play crysis at enthusiast settings at a resolution of 5870x1080 (although I can at 1920 x 1080). I want to be able to play crysis 2 maxed with the 5870 res, so I am guessing I am going to need to OC, am I rigt?
So am I going to need an aftermarket cooler to OC it that much. Right now the temps get to about low 60sC with crysis warhead at gamer settings at 5870 x1080 res.
Overclocking a 5850 to 5870 speeds will not make it as fast, the 5870 has more stream processors (1600 vs 1440). http://www.bjorn3d.com/read.php?cID=1702 is a tutorial you should definately check out, as it takes every aspect in detail.