SLI was used as Scan-Line Interleave by 3dfx at the beginning in 1998, 3dfx was later on bought by Nvidia. Nvidia still uses the name, SLI, however the technology has totally changed.

    SLI (Scalable Link Interface) is a technology which combines two or more graphics cards to produce a single output and allow users to install several GPUs (Graphics Processing Units) to increase the effect of the processing power for graphics. While rendering a 3D scene, having SLI can share the work load and makes the process work more smoothly. Nowadays, several games need two or more graphics cards to increase more effects to the gamers, so it makes SLI become an essential device.

    Usually, two graphics cards are installed in a motherboard, and they are set up in a master-slave configuration. The master card gives orders to the slave card, and the slave card will send the outputs back to the master card through a connector called the SLI Bridge. After the process, two images are combined to one and output the final render to the monitor.

    The SLI Bridge is used to reduce bandwidth constraints and help send data from the master card to the slave card. SLI Bridge can increase the speed between the GPUs up to 1GB per minute. Sometimes, SLI Bridge can be omitted, if the user uses a pair of low-end to mid-range graphics cards. Data can be delivered only through the chipsets on the motherboard because those graphics cards do not use that much bandwidth. Nevertheless, using SLI Bridge is essential if using high-end graphics cards since the chipset needs enough bandwidth to create the best effect.