Overclocking
Like with our HD2400/8400 roundup we used two tools to overclock the cards. For nVidia we used RivaTuner, which allowed us to monitor all the clock speeds, including the shader clock which is tied do the GPU speed. To overclock the ATI HD2600 we used AMD’s GPU Clock Tool, a utility that although very barren of advanced features is the only application that can modify the clocks of the new ATI cards.
The BFG card is overclocked right out of the box, similarly to the BFG 8600GTS we reviewed back on launch day. Because of that we didn’t expect much room for improvements. Getting from the already high 720MHz to the 783MHz was a nice surprise, as was the increase from 1107/2214MHz to 1139/2278MHz on the memory. The shader clock went from 1566MHz to 1674MHz.
Similarly the Gainward card with its out of the box increased clocks made us think we wouldn’t be able to push it much farther. Again we were proven wrong, as we managed to raise the GPU clock from 594MHz all the way to 700MHz (Shader clock went from 1296MHz to 1566MHz!) and the memory from 800/1600MHz to 830/1660MHz.
This leaves us with the ATI HD2600XT. Considering that we are reviewing a reference sample with its clocks set at default levels and the default cooler, we were relatively lucky in pushing the GPU clock from 800MHz to 850MHz and the memory from 1100/2200 to 1134/2268MHz.
The two nVidia cards despite being overclocked out of the box provided a pleasant performance increase when further overclocked by us. Would we have chosen to test the overclocked performance in less pixel shader intensive games the increases would have probably been less noticeable. The thing that surprised us the most here is the relatively low performance increase in Lost Planet. We can only guess that the shader clock increase did help, but was being held back by the rest of the graphics card calculations.
The ATI card benefited from the higher clocks as well and was able to stay well ahead of both nVidia cards in DX10 and to almost catch up to the DX9 performance of the “stock” BFG 8600GTS. All in all a very impressive showing.
The temperatures of the three cards during overclocking remained stable, only going a few degrees up due to our changes. The ATI card remained the coolest thanks to its slightly bigger cooler – it never went above 80°C even after an hour of stress testing. The two nVidia cards on the other hand peaked at 85°C for the BFG and 83°C for the Gainward card. Not bad, but we were slightly disappointed with the Gainward 8600GT as the relatively high temperature confirmed our suspicions that the cooler is only basic and the whole metal cage around the card serves aesthetics.
