The HIS version of the ATI Radeon HD 6990 - arguably the world's fastest graphics card - runs the dual-card solution at a slightly reduced clock speed, which can be reset to a single card's maximum speed if required
Traditionally, the release of a new graphics chip range was one of the more exciting events in the technology calendar. ATI and nVidia would start the ball rolling with their most mouth-watering product, a high-end fireworks display designed to shock and awe the public and whet the appetite.
Some months later, more modest variants would finally be unveiled, offering cut-down versions of the features-set, but aided by significantly reduced price tags that were genuinely affordable for the mainstream user.
However, with the 6900 series, ATI has turned this idea on its ahead, revealing its hand first of all with the relatively low-end 6950 (AMD codename: Cayman), before building up to the 6970 and, finally, the top-end 6990 - otherwise referred to by its codename, Antilles.
The HIS ATI Radeon HD 6990 is a mighty card, spanning around 303mm, and will need to be sited in a case with a lot of room around it. This card generates an awful lot of heat.
It also happens to be just about the noisiest card we've ever experienced. The thermal design power (TDP) of up to 375W (the 6970 is around 250W) hints at the amount of power required, and two 8-pin connectors will also need to be hooked up to the PSU.
The 6990's backplate is rather different from those on previous cards. While many products are packed with a number of full-size HDMI and DVI ports, the 6990 has just one of the latter, and no full-size HDMI at all.
Instead you get a quartet of Mini DisplayPort connectors. This does mean that the card can drive five screens at once, and dongles will be provided with the HIS to let you convert these ports into regular HDMI and DVI connections.
In reality, the 6990 isn't so much a new chip as it is two 6970s strapped together. As with previous dual-GPU solutions, the specifications have been reduced in order to keep the lid on the amount of heat generated, so you aren't getting the full raw speed from each chip.
This HIS version of the 6990, for example, runs at a core clock-rate of 830MHz, whereas HIS' standard 6970 employs a rate of 880MHz.
However, you can trigger the dual-BIOS switch on the card and push this clock speed up to its maximum 880MHz. This could result in the TDP rising to 450W, so you'll have to be rather well-informed or else reckless to really push the 6990 to its limits.
The memory is run at a speed of 1250MHz (5000MHz when the effective rate of the DDR GDDR5 memory is taken into account), as opposed to 1375MHz (5500MHz DDR effective) in the case of the 6970.
Indeed, the 6990's figures are only actually a slight improvement on those of the considerably cheaper 6950 - with core and memory clocks of 800MHz and 1250MHz (5000MHz DDR effective) respectively.
The memory complement is an eye-catching 4GB of GDDR5 memory, although you won't, in practice, get the full benefit from these 4GB. There are undoubtedly some eyebrow-raising figures though. The 3072 stream processors is astounding, as is the total of 48 SIMD engines.
Of course, the most fearsome features list is no use if the graphics chip falls down on real-world gaming performance. But there was never any question of this happening with the 6990.
Instead, what it unveiled was the most devastating set of benchmark figures we've seen, frequently around twice as fast as the 6950 at a resolution of 1920x1200.
It generally beats the GTX 590 too, only losing to the latter in Battleforge. Otherwise, the 6990 was king.
In Crysis, it polled 49.5 frames per second at 1900x1200, rather than the 47.1fps of the 590, and the 25.5fps of the humble 6950.
In Stalker: Call of Pripyat, it finished 7.6fps ahead of the GTX 590 (83.2 to 75.6fps), while more than doubling the 6950's figure of 38.1.
In the DX11 Heaven tests, it notched up 58fps at 1920x1200, just 2.7fps ahead of the GTX 590, but 29.9fps better off than the 6950.
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