NVIDIA has taken advantage of their leading position when it comes to multi-GPU technology, which they have introduced quite successfully some years ago. This technology was launched as SLI, Scalable Link Interface to bundle the performance of two graphics cards. SLI is a high-performance technology that intelligently combines and scales graphics performance and visual quality by having multiple NVIDIA GPU's in a single system. NVIDIA has puched once again the limits and instead of running two video cards together in SLI mode, they can now run four graphics processors in SLI mode, known as Quad SLI.

Update:
They removed the preview for some reason...