Overclocking

To find the maximum overclock of our card we used a combination of GPUTool and our benchmarking suite.
The overclocks listed here were achieved with the default fan and voltage settings as defined in the VGA BIOS. Please note that every single sample overclocks differently, that's why our results here can only serve as a guideline for what you can expect from your card.



The overclocks of our card are 835 MHz core (15% overclock) and 1260 MHz Memory (26% overclock). For your reference, the defaults are 725 / 1000 (GPU-Z is showing the wrong values due to a bug which will be fixed in the next version). As a percentage those overclocks are really nice. The maximum core clock of 835 MHz is clear evidence that this GPU ended on a HD 5850 because it could not handle the HD 5870 clock speeds of 850 MHz. The memory chips are exactly the same as on the HD 5870, which results in roughly the same maximum memory clock. In essence you can get a HD 5850 and overclock it to almost HD 5870 performance levels in just a few minutes.


I would also like to point out that you can increase the voltage for better GPU overclocking. The default voltage of 1.09 V is quite low and there is plenty temperature headroom as well. So I ran a quick test at 1.30 V GPU and reached a maximum core clock of 1000 MHz.

As mentioned in the HD 5870 article, overclocking the memory on these cards is quite different from any other card so far. Normally you'd expect rendering errors or crashes, but not with these cards. Thanks to the new error correction algorithm in the memory controller, every memory error is just retransmitted until everything is fine. So once you exceed the "stable" clock frequency, memory errors will appear more often, get retransmitted, but the rendered output will still look perfectly fine. The only difference is that performance drops, the further you increase the clocks, the lower the performance gets. As a result a normal "artifact scanning" approach to memory overclocking on the HD 5800 Series will not work. You have to manually increase the clocks and observe the framerate until you find the point where performance drops.

I also checked whether it is possible to enable the disabled shaders, but to no avail. The shaders are locked using the same method as on the HD 4830 for example - there is no known method to unlock them.

Overclocked Performance

Using these clock frequencies (835 / 1260) we ran a quick test of Call of Duty 4 to evaluate the gains from overclocking.


The actual 3D performance gained from overclocking is 14.6%.

Temperatures

Temperatures look excellent. Even with overclocking the temperature is comfortably cool. As (almost) always I'd personally liked to see higher temperatures and less fan noise. But fan noise is quite acceptable as it is right now, so no big deal.