Just how good is this rare beast of a card?

When we took a look at the reference version of AMD’s Radeon HD 6990, we found a board that was impressive on a number of fronts, though not all the impressions were positive. The HD 6990 builds in two full Radeon HD 6970 GPUs onto a single board, each with its own 2GB of frame buffer. In our initial testing, performance looked to be very fast, but the reference board was also pretty noisy under load.
So we waited to get a shipping board from one of AMD’s many board partners in order to formally review a real product. And we waited. And waited some more. (Bear in mind that availability of Nvidia’s GTX 590 isn’t much better.)
At last, XFX shipped us an actual retail Radeon HD 6990, so we’re finally able to render a verdict on AMD’s killer card. Before we dive into benchmarks and observations, it’s worth recapping the specs and features of the card, and its GPUs.
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