OverclockingObviously each individual card of any model can react differently when overclocked but we tried to push all the cards in our possession so as to be able to observe any generalities. We used Furmark to load the cards to a maxiumum and insured stability by only increasing the clock by 5 MHz.
Note that GDDR5 memory has different mechanisms for the detection of errors which mean that in case of significant overclocking, the memory is stable but loses a lot of time reparing any linked errors, either by sending corrupted data back or recalibrating its clocks. We noted a very rapid drop in performance, in general with 50 MHz overclocking and in certain cases even with just 25 MHz. We therefore abstained from overclocking the memory.
Here are the clocks we managed to reach:
The GF104 which these GeForce GTX 460s are based on, can easily be overclocked and, in general, easily attains 800 MHz. We managed to stabilise all the cards at between 825 and 875 MHz, without any correlation between the base clock of the factory overclocked models and the maximum stable clock.
In order that a maximum number of GF104s qualify at a certain spec level, NVIDIA varies the GPU voltage in load between various models. Increasing this voltage slightly means certain capricious samples can be recovered and lowering it slightly allows NVIDIA to validate other samples with higher leakage. At idle, all the cards are at 0.875.
When you look at these numbers, don't forget that huge overclocking can put a lot of stress on the power stages. Stability is therefore not always guaranteed (with poor cooling inside the casing) and it could damage the board in the long run. Some boards such as the Asus TOP (4 phases), the Gigabyte SOC (6 phases) and the MSI Hawk (6 phases), are better suited for huge overclocking than the other boards which have to make do with 3 phases to power the GPU. We advise you not to go over 800 MHz with these ones.
For info, we observed the performance of all the cards at their original clocks and when overclocked in Crysis Warhead, at 1920x1200 with 4x antialiasing and in Gamer mode.
In comparison to the stock clocks, we gained up to 26% with overclocking! These are unusual gains, especially as even in the worst cases we gained 15% all said and done.
At the original clocks, it’s no surprise to see the Gigabyte SOC model and the Zotac AMP! in the lead with a gain of 17% on the stock model.