Editing Scalable Link Interface (section)

==Implementation==
SLI allows two, three, or four [[graphics processing unit]]s (GPUs) to share the workload when rendering [[Real-time computer graphics|real-time]] [[3D computer graphics]]. Ideally, identical GPUs are installed on the motherboard that contains enough [[PCI Express]] slots, set up in a [[Master/slave (technology)|master–slave]] configuration. All graphics cards are given an equal workload to render, but the final output of each card is sent to the master card via a connector called the SLI bridge. For example, in a two graphics card setup, the master works on the top half of the scene, the slave the bottom half. Once the slave is done, it sends its render to the master to combine into one image before sending it to the monitor.

The SLI bridge is used to reduce bandwidth constraints and send data between both graphics cards directly. It is possible to run SLI without using the bridge connector on a pair of low-end to mid-range graphics cards (e.g., 7100GS or 6600GT) with Nvidia's Forceware drivers 80.XX or later. Since these graphics cards do not use as much bandwidth, data can be relayed through just the [[chipsets]] on the motherboard. However, if there are two high-end graphics cards installed and the SLI bridge is omitted, the performance will suffer severely, as the chipset does not have enough bandwidth.

Configurations include:
* Two-way, three-way, and four-way SLI uses two, three, or four individual graphics cards respectively. 
* Two GPUs on one graphics card. Examples include the GeForce GTX 590, the GeForce GTX 690 and the GeForce GTX Titan Z. This configuration has the advantage of implementing two-way SLI, while only occupying one PCI Express slot and (usually) two expansion I/O slots. This also allows for four-way SLI using only two cards (which is referred to as Quad SLI).

Nvidia has created a set of custom [[video game]] profiles in cooperation with video game publishers that will automatically enable SLI in the mode that gives the largest performance boost.

Nvidia has three types of SLI bridges:
*Standard bridge (400&nbsp;MHz pixel clock<ref>{{cite web|url=http://www.overclock.net/t/1550293/evga-new-pro-sli-bridges-v2/50#post_23775474|title=[EVGA] New Pro SLI Bridges V2|website=Overclock.net|date=22 February 2016 }}</ref> and 1&nbsp;GB/s bandwidth<ref>{{cite web|url=http://www.geforce.com/hardware/technology/sli/faq#g1|title=SLI - FAQ - GeForce|website=www.geforce.com}}</ref>)
*LED bridge (540&nbsp;MHz pixel clock<ref>{{cite web|url=http://www.overclock.net/t/1550293/evga-new-pro-sli-bridges-v2/50#post_23775443|title=[EVGA] New Pro SLI Bridges V2|website=Overclock.net|date=22 February 2016 }}</ref>)
*High-bandwidth bridge (650&nbsp;MHz pixel clock and 2&nbsp;GB/s bandwidth<ref>{{cite web|url=http://www.tomshardware.com/reviews/nvidia-geforce-gtx-1080-pascal,4572-4.html|title=Nvidia GeForce GTX 1080 Pascal Display Pipeline & SLI|date=17 May 2016}}</ref>)

The standard bridge is traditionally included with motherboards that support SLI and is recommended for monitors up to 1920×1080 and 2560×1440 at 60&nbsp;Hz. The LED bridge is sold by Nvidia,<ref>{{cite web|url=http://www.geforce.com/hardware/technology/sli/bridges|title=NVIDIA SLI Bridges - GeForce|website=www.geforce.com}}</ref> EVGA,<ref>{{cite web|url=http://www.evga.com/articles/00919/EVGA-Pro-SLI-Bridges-V2/|title=EVGA - Articles - EVGA Pro SLI Bridges V2|publisher=EVGA}}</ref> and others and is recommended for monitors up to 2560×1440 at 120&nbsp;Hz and above and 4K. The LED bridges can only function at the increased pixel clock if the GPU supports that clock. The high-bandwidth bridge is only sold by Nvidia<ref>{{cite web|url=http://www.geforce.com/hardware/10series/geforce-gtx-1080|title=GeForce GTX 1080 Graphics Cards from NVIDIA GeForce|publisher=Nvidia}}</ref> and is recommended for monitors up to 5K and surround.

The following table provides an overview on the maximum theoretical bandwidth for data transfers depending on bridge type specifications as found on the open market:<ref>{{Cite web|url=https://www.pcgameshardware.de/Pascal-Codename-265448/News/HB-SLI-Bruecke-Unterschiede-1204297/|title = Nvidia HB-SLI-Brücke: Unterschiede anhand von Röntgenbildern gezeigt|language=de|date = 12 August 2016}}</ref>
{| class="wikitable"
|-
! Clock rate !! 400&nbsp;MHz !! 540&nbsp;MHz !! 650&nbsp;MHz
|-
| single channel || 1 GB/s || 1.35 GB/s || 1.625 GB/s
|-
| dual channel || 2 GB/s || 2.7 GB/s || 3.25 GB/s
|}