With the appearance of the PCI Express x16 bus architecture, NVidia realized that the main idea of using DUAL GPUs to share the load of today's high demand graphical environments could be applied once again, with amazing results. As NVidia says: NVIDIA® SLI™ (Scalable Link Interface) technology is a revolutionary approach to scalability and increased performance. NVIDIA SLI takes advantage of the increased bandwidth of the PCI Express™ bus architecture, and features hardware and software innovations within NVIDIA GPUs (graphics processing units) and NVIDIA MCPs (media and communications processors). Together the NVIDIA SLI patent-pending technologies work seamlessly to deliver heart-pounding PC performance. And depending on the application, NVIDIA SLI can deliver as much as 2x the performance of a single GPU configuration for unparalleled gaming experiences.

The proportion of GPU load that will be handled by each card is controlled by the nVidia driver. However, a drawback of this technology is that the performance of the system is driver dependent. nVidia provides several gaming profiles with each new driver release to improve the performance of any SLI system.

SLI is enabled through the device driver that is provided with the retail package or from nVidia's web site .

When SLI is enabled for the first time, you will see the following warning message:

At this point, you must use the primary graphics card for the monitor signal.

You can also choose to see the GPU load for each card. This overlays a green vertical bar on your screen that changes according to the load. The snapshot below is taken under heavy load, during 3DMark05 testing.