Overclocking

We initially tried the Overdrive tool of the Catalyst Control Center, but the slider would only allow us to push the GPU from 750MHz to 790MHz, which is a fairly poxy overclock. We therefore switched to RivaTuner to squeeze as much extra frequency as we could from the chip.

With such an effective cooler, we started high with our initial overclock, but hit immediate stability problems at 875MHz. The card was stable at 790MHz, so we pushed up from there until we finally hit 810MHz on the GPU - not a bad overclock from 750MHz, but not the best we've seen from a Radeon HD 4870 either.

Being a bit more conservative with the memory (remember that half of it isn't directly cooled) we managed to push up from 900MHz (3,600MHz effective) to 985MHz (3,940MHz effective). This boosted the memory bandwidth from 115.3GB/s to 126.08GB/s



The extra frequency gave us a bit of extra speed in Crysis, but not so much extra that it made much difference. At neither of our standard test resolutions did the game turn from unplayable to playable - minimums of 16fps and 17fps are too jittery for us. Of course, overclocking is a case-by-case thing and clearly the cooler of this card can handle a big overclock provided that the GPU can too.