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 demanding graphical environments can 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 graphics load that the two GPUs undertake is not always the same. You can see that the graphics load in our example above, is not 50% for both GPUs. nVidia uses advanced dynamic load balancing algorithms that are responsible for sharing the load in two. This is a very clever approach, since in most games and applications, the upper part of an image might need more processing power than the lower. Having that in mind, NVidia decided to share GPU load according to GPU power needs of the game/application.

NVidia uses a digital SLI connector (3dfx's connectors were analog connectors) to connect the two cards. You will find this connector provided by ASUS in the retail package.

On the other hand, power requirements increase since the two GPUs need more power to function efficiently. The following table states the power requirements suggested by ASUS.

According to NVidia, available GPUs featuring SLI support are GeForce 6800 Ultra, GeForce 6800 GT, GeForce 6800 and GeForce 6600 GT GPUs. On the other hand, ASUS released a list of certified add-in SLI VGA cards that are recommended for the A8N-SLI Deluxe. This list is shown below:

You can always find more information about the Scalable Link Interface at the NVidia web page.