Back in November when AMD brought OCC out to LA for the 6 series launch event, the HD 6990 Antilles was not much more than a footnote in the presentation as an all new "Future Product". A product we were told not to talk about as it was under NDA with more information to be forthcoming. Here we are a few months later with that product ready for review. Today we have the Sapphire HD 6990. AMD has held onto the single card performance title since the introduction of the HD 5970 while NVIDIA steadily chipped away at that lead as they refined their Fermi architecture to the point of delivering a card (in the form of the GTX 580) that took back the single GPU card title that AMD had hoped to capture with the HD 6970. Being just "good enough" is no longer acceptable and with this launch AMD has pushed the envelope in terms of the thermals and power consumption to make the HD 6990 a point of difference and deliver game changing performance much the same way the HD 4870x2 and HD 5970 did.Under the hood, the HD 6990 is nothing more than a pair of HD 6970 Cayman GPU cores that have been binned for low leakage ASICs and downclocked to meet the temperature and power commitments of the card's design. The HD5970 was built to fit into a 300 watt profile while the HD 6990 is designed to fit into a 375 watt profile with the ability to bump up to 450 watts via the AUSUM switch. This switch (used on all HD 69XX series cards) now gets a new function as an overclocking switch that loads a new voltage and clock speed profile. Something the HD 5970 lacked. This one change bumps the core clock speed and voltage up to meet HD 6970 clock speeds of 880MHz from the standard, as delivered HD 6990 clock speed of 830MHz. More changes that include refining the cooling design and voltage circuits promises a new take on the dual GPU, single PCB, video card. Let's take a look at what AMD and Sapphire now have to offer with their upper crust HD 6990.