Introduction
History suggests that dual-GPU graphics cards are all about optimum performance and maximum bragging rights. Recent examples - including the AMD Radeon HD 6990 and NVIDIA GeForce GTX 590 - unite two top-end GPUs on a single PCB in order to contend for the title of world's fastest graphics card.
They're mighty impressive products, but pricing in excess of £500 puts them out of reach of most consumers. So what would happen if a manufacturer opted to pair two cheaper GPUs in an effort to hit a more realistic price point of around £300? Turns out that's exactly what PowerColor decided to do, and it created this:
Dubbed the Radeon HD 6870 X2, this custom-designed beastie features a duo of AMD's upper mid-range 6870 graphics processing units - codenamed Barts - hooked up internally via CrossFire to give the power of two.
Independently, the Radeon HD 6870 is far from being the quickest GPU available, but two of them running in tandem does result in some tantalising numbers. Doubling up on AMD's reference design, this here card provides two GPUs running at 900MHz apiece, a total of 2,240 stream processors, 112 texture units and 64 ROPs. On top of that, each GPU is hooked up to 1GB of GDDR5 memory via a 256-bit interface, resulting in 2GB of total on-board memory.
The numbers suggest that the Radeon HD 6870 X2 will be faster than any single-GPU graphics card currently on the market. And it'll be cheaper, too. While NVIDIA's single-GPU GeForce GTX 580 will set you back somewhere in the region of £350, PowerColor's touting a suggested retail price of £314 for the dual-GPU 6870 X2 and it's throwing in a free copy of DiRT 3, too.
This is a card that clearly has the GTX 580 in its firing line, but there's a small problem with the suggested retail price - you could go out and buy two standard Radeon HD 6870s and pair them in CrossFire at a cost of roughly £280. So, aside from the bundled game, why pay more?
The simple answer would be convenience. By pairing two GPUs on a single PCB, PowerColor's Radeon HD 6870 X2 requires only a single PCIe x16 slot, and if you've only two slots available, this then leaves room for future upgrades.
But there are disadvantages, too. In order to squeeze all of the components onto one card, the length of the 6870 X2 has been stretched to 300mm (some 50mm longer than a standard 6870) and two eight-pin PCIe power connectors are required to keep both GPUs topped up with juice.
What's also interesting is that PowerColor has opted to use a Lucid bridge chip to pair the two on-board GPUs in favour of the traditional AMD/PLX solution. PowerColor has told us that the "Lucid bridge chip has much better availability with lower price," and adds that "the performance difference is not considerable".
Then there's the small matter of cooling. Two GPUs on a single PCB are a recipe for heat, so PowerColor has conjured up an impressive heatsink that's tasked with keeping both chips in check. Each GPU makes direct contact with three ultra-thick copper heatpipes, and these are then routed to a card-long array of aluminium fans that's cooled by two PWM fans.
The heatsink looks impressive, but the exterior plastic shroud does feel a little flimsy - and it's probably that thin shell that helps keep the card's total weight down to 858g. For reference's sake, that's actually lighter than a single Radeon HD 6870, which tips our scales at 903g.
Intrigued? We were, so read on to find out how the 6870 X2 stands up to today's range of high-end competitors.
