Overclocking

To find the maximum overclock of our card we used a combination of Rivatuner, ATITool's successor, AMD internal software, Furmark and our benchmarking suite.



The final overclocks of our card are 762 MHz core (22% overclock) and 1138 MHz Memory (15% overclock). This frequency is the highest clock frequency at which both GPUs are stable. To achieve optimum performance you must ensure that both GPUs run at the same core and memory clocks. Both overclocks are very impressive, I expected much less because of the high heat density on these cards. Apparently there is still some headroom left in the HD 4850 X2. Unfortunately the overclocking process is very complex, compared to other cards. First you need to find an overclocking program that works with the HD 4850 X2 and can overclock both cores. Next you need to find a stress test that properly loads the card so you can check if it's stable. Since CF does not work in windowed 3D, you constantly have to switch between fullscreen and your overclocking program to change clocks.

Overclocked Performance

Using these clock frequencies we ran a quick test of Call of Duty 4 to evaluate the gains from overclocking.


The actual 3D performance gained is 15%.

Temperatures

The card runs at very reasonable temperatures in both idle and load. Unfortunately the fan is very very noisy.