Final thoughts and rating
We're going to couch the conclusion with the usual caveat that applies to multi-GPU graphics-card setups: you may not always experience considerable frame-rate improvements in lesser-known titles. Multi-GPU driver support is constantly evolving and liable to be not quite as robust as that for a single card.That said, the latest graphics cards from AMD and NVIDIA exhibit excellent scaling when adding another card to the system. Our numbers show that two Radeon HD 6850s provide a 1.9x boost to a single-card's performance - improvements that are also mirrored by a GeForce GTX 460 1,024MB couple in SLI.
Radeon HD 6850 scaling is good enough for us to stop recommending the Radeon HD 5850 XF or single-card HD 5970 - unless you only have one PCIe x16 slot in the motherboard. The new GPUs produce near-identical performance to last year's best but do so at a substantially lower price and with lower power-draw.
Moreover, HD 6850 XF blows a single Radeon HD 5870 - costing just a little bit less - out of the water. Recommended without reservation, then? Not quite, as NVIDIA's own £300 multi-GPU setup, comprising of two GeForce GTX 460 1,024MB in SLI, performs just as well as AMD's setup, and it opens up the way to 3D Vision Surround, should you want to go down that route.
But we're going to sit on the fence for a short while yet before outright recommending either the HD 6850 XF or GTX 460 1GB SLI. That fence has the name of Radeon HD 6970 firmly etched on it, and if the leaked performance numbers are anything to go by, the single-GPU 'Cayman' card may upset the rather attractive multi-GPU apple cart.
Bottom line: AMD has improved its CrossFireX scaling to match NVIDIA's. Two Radeon HD 6850s, coming in at £300, offer excellent performance with enviable power-draw characteristics. Cayman, over to you.
The Good
Near-double performance from two cards
Low-ish power-draw
Attractive retail price makes HD 5850 XF and HD 5970 redundant
The Bad
Multi-GPU scaling has its own particular foibles
HEXUS Rating
HEXUS Awards
AMD
Radeon HD 6850
1,024MB in CrossFireX
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