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Sapphire HD 4870 X2 2048 MB |
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Overclocking
To find the maximum overclock of our card we used a combination of AMD internal overclocking software and our benchmarking suite.
The final overclocks of our card are 795 MHz core (6% overclock) and 960 MHz Memory (7% overclock). Both overclocks are slim, but were to be expected given the heat output of this dual GPU monster. Please note that we always set both cards to run at the same clock speeds, that's the configuration that offers best performance.
Overclocking the HD 4870 X2 is very complicated I must say. Using CCC gives you very tight OC limits of 800 MHz on core and 1000 MHz on memory. Since the card is using a dual GPU design there are also two BIOSes on the card. So if you plan on using a BIOS editor, you have to edit both BIOSes.
Stability testing with ATITool or Furmark does not work reliably because ATITool runs in a window (always 500/500 and no CrossFire, see the "Power Consumption" page of this review). Furmark runs fullscreen 3D but only in single GPU mode. Let's hope a future driver fixes all these problems.
Temperatures
Wow, that's a lot of temperatures to look at. We can clearly see that the second GPU runs cooler under load, whether this is because load distribution or design of the cooler remains unknown. Even when overclocked the temperatures stay within an acceptable range given the power draw of the card.
The three temperatures are all different on-die sensors located at Display IO (#1), Memory IO (#2) and Shader Core (#3).
