Conclusion

Our attempt to overclock the ATI Radeon HD 3870 to an extremely high clock rate proved that this GPU should not be expected to increase its performance dramatically if its frequency is increased by 30%.

Click to enlarge

Click to enlarge

The diagrams show that the performance benefits are small. The overclocked Radeon HD 3870, working at its limit, often fails to reach the level of the GeForce 8800 GT 512MB. For example, the speed of Crysis in DirectX 10 mode and at the highest quality settings increases by 20% but that only means that the frame rate grows from 15 to 18fps. The more advanced GPUs delivered higher performance anyway. The same is true for other DirectX 10 applications such as Call of Juarez, Lost Planet and World in Conflict. On the other hand, the extreme overclocking helped achieve acceptable performance at least at 1280x1024 in such games as Call of Duty 4 and  S.T.A.L.K.E.R. and improved the average frame rate in some other games.

You should be aware that these performance benefits are achieved by means of heavy overclocking that can’t be harmless whereas installing a more advanced cooling solution would require an additional investment.

The dual-processor Radeon HD 3870 X2, consuming about the same amount of power, beats the GeForce 9800 GTX where AFR support is implemented properly. The more affordable GeForce 8800 GTS beats the overclocked Radeon HD 3870.

The lack of linear performance growth at overclocking is due to many factors such as architectural features of the GPU (the lack of texture filter or rasterization units), driver flaws, insufficient application-specific optimizations, etc. This cannot justify the result, though.

Although TSMC’s 55nm tech process developed in collaboration with ATI/AMD has a good frequency potential and RV670-based cards can work at a frequency of 900MHz quite easily, there is no sense in releasing Radeon HD 3870 with increased frequencies. There can be a higher performance growth if each of the chip’s 26 frequencies is increased, perhaps not proportionally, but it is not required: the new ATI RV770 chip is already here.

Summing it up, extreme overclocking is only really interesting for overclocking communities and for setting records. It is a kind of sport, actually. This sport may be exciting and spectacular, especially if practiced with exotic tools like liquid nitrogen, but has little practical value.