Design

AMD Radeon HD 6990
GPU: 2 x Radeon HD 6970 (Cayman) Interface: PCIe x16 GPU clock rate (ROPs/shaders): 830-880/830-880 MHz (standard) Memory clock rate, physical (effective): 1250 (5000) MHz (standard) Bus: 2 x 256-bit Stream processors: 2 x 1536 TMUs: 2 x 96 (BLF/TLF/ANIS) ROPs: 2 x 32 Size: 330x100x33 mm PCB color: black RAMDACs/TDMS: integrated into GPU Outputs: 1 x Dual-Link DVI, 4 x mini DisplayPort 1.2 Multi-GPU mode: hardware CrossFireX

Comparison with the reference design, front view
AMD Radeon HD 6990	Reference AMD Radeon HD 5970

Comparison with the reference design, rear view
AMD Radeon HD 6990	Reference AMD Radeon HD 5970

We compared HD 6990 with HD 5970 for a reason. Both cards have similar outward architecture: 2 GPUs, 2 x 256-bit memory buses. And yet we can see that HD 6990 is quite different from the predecessor. The GPU is still surrounded by memory modules, but those are now closer to edges. And in the center is a new-generation power supply unit, which is understandable because the card can consume as much as 420 W, meaning very high currents and the need to shield high-frequency GPUs from noise. Power supply elements require adequate cooling, too. The card is as long as HD 5970, which is ridiculous in itself. But, well, the fastest graphics requires a big enclosure.

The card has two 8-pin supplementary power connectors.

Maximum resolutions and frequencies:

• 240 Hz maximum refresh rate
• 2560 x 1600 @ 60Hz max. digital resolution
• 2048 x 1536 @ 85Hz max. VGA resolution

Cooling

AMD Radeon HD 6990
Card's high power consumption and layout demands a specially designed cooler with a fan in the middle. Each core is covered with copper finned heatsinks with vaporizing chambers. These are united into a single cooling solution that also covers power elements in the center of the PCB. The fan drives air in two opposite directions to cool down the heatsinks. Note that to improve heat transfer AMD uses special thermal interfaces between chips and heatsinks. And these are very fragile and, essentially, one-time only. So AMD doesn't recommend to remove the cooler — you may not get the same cooling efficiency afterwards. Speaking of noise, it's quite high in the heavy 3D mode, because the fan rotates very fast. In turn, there's no noise in the 2D or light 3D mode.

Traditionally, we monitored temperatures using EVGA Precision (based on RivaTuner).

AMD Radeon HD 6990, 830 MHz

AMD Radeon HD 6990, 880 MHz

As you can see, despite colossal power consumption, the core temperatures don't exceed 90°C, so the cooler is efficient enough. Speaking of values, the power consumption is 418 W while overclocked and 360 W in the regular mode, so make sure you have a decent power supply.

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