AMD introduced its first Radeon HD 6000 graphics card last October, when we reviewed the mid-range Radeon HD 6870. Since then AMD opened up to show its GPU roadmap and the cards that soon thereafter were coming to market.The high-end Radeon HD 6970 and HD 6950 also arrived late last year, while the dual-GPU version of AMD's last generation graphics series code-named Antilles was expected to arrive shortly after. Coincidentally (or not) both AMD and Nvidia took a few months longer than expected to show its hardcore dual-GPU graphics cards, with the former making the first move to finally unveil the Radeon HD 6990.Having looked at most of the previous generation Crossfire and SLI products, we were certainly looking forward to see what AMD had in store for us with this dual-GPU monster.We don't think AMD sells large volumes of these dual-GPU cards, in fact, previous versions of their topmost offerings have been known to disappear from retail temporarily and then stock back up again. Having that said, the Radeon HD 6990 is an important product on AMD's line-up as it can do a lot for the series reputation, just as the HD 5970 did before.