Overclocking

To find the maximum overclock of our card we used a combination of GPUTool and our benchmarking suite.
The overclocks listed in this section 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. We turned off ULPS for all overclocking testing, clocks were synchronized on both GPUs.



The overclocks of our card are 910 MHz core (10% overclock) and 1525 MHz Memory (22% overclock). I was quite surprised to see that much overclocking potential on the HD 6990. An extra 10% on the GPU, that directly translates into extra heat, is very respectable. The memory overclock is good too, but memory overclocking typically does not add that much heat, so the results here are about the same as on a single GPU card.

Overclocked Performance

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


The actual 3D performance gained from overclocking is 9%.

Temperatures

Temperatures look well optimized to keep the card at safe operating levels, while minimizing the emitted fan noise.

Clock Profiles

Modern graphics cards have several clock profiles that are selected to balance power draw and performance requirements.
The following table lists the clock settings for major performance scenarios and the GPU voltage that we measured. We measure on the pins of a coil or capacitor near the GPU voltage regulator.