nterface) A multi-GPU interface from NVIDIA for connecting two or four NVIDIA graphics cards together for faster rendering on one or two monitors. SLI machines require adjacent PCI Express slots, NVIDIA's Media and Communications Processor (MCP) on the motherboard and identical SLI-certified NVIDIA graphics cards. Such cards come with an SLI connector that connects one card to the other. See multi-GPU
Using Quad SLI, the power of four NVIDIA graphics cards is harnessed to provide extraordinary rendering for gaming. The arrows point to the two SLI connectors that tie the boards together.