SLI GPUs
NVIDIA SLI GPUs deliver powerful, elegant and super-rich graphics for games and other graphics-intensive applications. Combining two NVIDIA SLI-certified graphics cards in a single system allows you to essentially double your graphics performance (up to 2x). NVIDIA SLI-certified GPUs feature dedicated, built-in SLI hardware and take advantage of the additional bandwidth of the PCI Express bus architecture. Connected by the SLI connector, each GPU has a maximized connection pathway, and can leverage the second card for reaching top-speed performances on a single display. Professional users can also take advantage of SLI technology on dual NVIDIA Quadro GPUs to span an OpenGL window across multiple displays. Unlike previous dual-card solutions, NVIDIA SLI can output in both digital and analog formats for the highest image quality.

SLI Motherboards
NVIDIA SLI-certified motherboards include NVIDIA MCPs and are designed to deliver the highest levels of performance in PCI Express, multi-GPU platforms. Additionally, NVIDIA nForce SLI-certified motherboards balance the bandwidth from the PCI Express bus architecture between both GPUs for over-the-top graphics, great speed, and scaled performance.

How it Works
An NVIDIA SLI system includes a PCI Express motherboard that supports two physical connectors that are capable of having two NVIDIA-based PCI Express graphics cards plugged into them. Joined by the NVIDIA SLI connector, the two graphics cards power one monitor, delivering earth-shattering PC performance. Screenshot courtesy of 3DMARK03.