When they first tried ASUS' new GTX 670 Direct CU II with 4GB of memory on its own, [H]ard|OCP had difficulty recommending it over a 7970 but they planned to try two cards in SLI to see if that would improve the comparative performance.  The competitors are a pair of 2GB 670s, a pair of 3GB HD7970's, a pair of 2GB 680s and of course two 4GB 670s, all powering a system at 5760×1200.  Unfortunately the quote from the conclusions spells out the results "It's like putting beefy off-road tires on a Yugo", so while it will give you the ability to use some higher graphics settings, overall you are still better of with HD7970s or GTX680s.

"We review two ASUS GeForce GTX 670 DirectCU II 4GB video cards in SLI under NV Surround resolutions. We'll answer the question as to the value and validity of 4GB of RAM on a GeForce GTX 670 GPU video card in SLI. Far Cry 3, Hitman Absolution, and all our other games will be taken to the extreme to get to the bottom of 4GB GTX 670 cards."

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