Only 2-Way SLI Setups Officially Supported By Nvidia GTX 10 Series
Rumors have been circling around the Internet that Nvidia is dropping its support for 3-way and 4-way SLI Multi GPU setups, and will release a high bandwidth bridges that would limit the SLI support to just two cards.
The new SLI HB connectors use both SLI connectors on a Geforce graphics card, which allows them to transfer data at 650 MHz, which is significantly increased compared to 400 MHz that traditional SLI bridges run at.
These High Bandwidth connectors allow GPUs to deliver a smoother gaming experience at 4K or above resolutions and on multi-monitor Nvidia Surround setup. This of course limits the SLI configuration to 2 GPUs and Nvidia says that it’s for the best.
According to GTX 1080 whitepaper:
By default, GeForce GTX 1080 SLI supports up to two GPUs. 3-Way and 4-Way SLI modes are no longer recommended. As games have evolved, it is becoming increasingly difficult for these SLI modes to provide beneficial performance scaling for end users. For instance, many games become bottlenecked by the CPU when running 3-Way and 4-Way SLI, and games are increasingly using techniques that make it very difficult to extract frame-to-frame parallelism.
Now this does not mean that consumers will not be able to use 3-way or 4-way SLI, they certainly can. The reason why Nvidia suggests that only two GPUs are supported in SLI for GTX 10 series is that, traditionally 3-way and 4-way SLI setups do not give the theoretical or desired results. In fact, these 3-way or above configurations diminish the performance of the system.
However, 2-way SLI setups gives the ideal results that a PC enthusiast wants, and that is the reason that Nvidia only supports 2-way SLI setups.
Nvidia has said that developers can support 3-way SLI manually using DirectX 12 multi-display adapter and explicit linked display adapter modes.