It is March 8th, and as we reported last week, the AMD Radeon HD 6990 is being released today. The Radeon HD 6990 has two Caymen GPUs. This is the same GPU found in the Radeon HD 6970. Essentially, the 6990 is running on-board CrossFire between the two GPUs. This gives it 3072 stream processors (2 x 1536), 192 texture units (2 x 96), and 4GB of GDDR5 (2 x 2 GB).

The 6990 will have a core speed of 830 MHz and an effective memory clock of 5.0 GHz. This makes the 6990 a tad slower than the single GPU 6970 which had clock speeds of 880 MHz on the core, and 5.5 GHz for the memory. Since this is the only difference between the 6990 and the 6970, one would expect that a 6990 would perform similarly to a pair of 6970’s in CrossFire.

The 6990 is very interesting in one respect. While the card idles at 37 Watts, when the graphics card is fully loaded, it consumes 375 Watts. This is outside the PCIe specifications. It makes the 6990 the most power hungry graphics card to date. To handle that heat, AMD has redesigned the heat sink. On the 6990, the fan is located in the middle of the graphics card, and each GPU on the 6990 has its own heat sink that is isolated from the other one. This allows the 6990 to dissipate over 450 Watts of thermal energy.

As mentioned, the 6990 is outside the PCIe specifications. It has two 8 pin power connectors, each of which can deliver 150 Watts. It can also draw up to 75 Watts from the PCIe connector. This means that it can, and will, draw 375 Watts. But that is not quite the whole story. Remember PowerTune? It allows AMD to control how much power the graphics card consumes. If the graphics card tries to draw too much power, PowerTune will throttle back the clock speeds to keep the card within specifications. In this case, PowerTune keeps the 6990 at 375 Watts. Most games will not be throttle back. However, there may be some games that are.

Did I mention that the 6990 is outside the PCIe specifications? To help the graphics card meet its energy budget, AMD is using cherry picked GPUs that run at a lower default clock voltage. Also to help reduce power consumption, AMD is using less expensive 5 GHz GDDR5 memory. This memory runs at a lower memory voltage than the 6 GHZ GDDR5 memory found on the 6970.

But who wants to run a stock 6990. Literally with the flick of a switch, you can run the 6990 at the same default clock speeds as the 6970. The 6990 comes with a physical switch that allows you to switch between the default BIOS that has a 830 MHz core speed, and a performance BIOS that comes at 880 MHz core speed. This will, of course, consume more power than 375 Watts. Fortunately the cooler can handle it. The question remains to whether or not the power supply in your system can handle it, as well as the increased thermal loads on the rest of the components in your system.

Anandtech has posted an in-depth review of the 6990. Here is what they thought of it:

Dual-GPU cards have always been a niche product, but the 6990 really takes this and runs with it. There’s no significant power/noise savings to be found by consolidating 2 GPUs on to a single card, and as we said earlier with the dual-exhaust cooler the 6990 is effectively 2 video cards on one PCB. This isn’t a bad thing – the 6990 is the world’s fastest video card after all – but it drives the card in to some very specific niches. If you fall in to these niches, then the 6990 is certainly the card for you.

The launch price for the 6990 is $699. This is going to be one expensive graphics card.

via : AMD’s Radeon HD 6990: The New Single Card King @ Anandtech

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