"Quad SLI is NVIDIA's ultimate answer to AMD's CrossFireX. Four G92 chips working together to create the optimal gaming experience and beat a pair of Radeon HD 3870X2, that's theory at least. Quad SLI wasn't ready when GeForce 9800GX2 was launched, but now, a few days later, the power that is Quad SLI has arrived. Several reviews are up, and they all show quit similar results, mainly due to one common nominator with all test systems.
While Quad SLI is certainly powerful, it also requires a CPU running at high frequencies to really shine. We haven't seen any review with a CPU running at frequencies beyond 3.2GHz, and that's no way near enough. Anandtech used a Skulltrail platform, but four additional cores won't help you much, when what you really need is higher frequency. Skulltrail is the only platform that can run both Quad SLI and CrossFireX though, but we would've preferred seeing the processors running at 3.5-4GHz, at least."