Iria

Eighteen months ago when nVidia's GeForce 8800 GTX was king of the hill, a multi-GPU setup was either ostentatious and reserved only for the most die hard gamer if you were using a high-end card, or downright silly if you were pairing up midrange and lower. NVIDIA's SLi initiative, started back with the GeForce 6 series, was basically a kludge designed to wring that last ounce of performance out of the cards of the era for the deep-pocketed enthusiasts. ATI's CrossFire, when it debuted up until the release of the Radeon X1950 Pro, was an embarassment, offering poorer performance and compatibility than NVIDIA's solution.
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Source: Benchmark Reviews