Quote:In a surprising turn of events, Nvidia today announced that it's completely killed its current model of SLI, which lets your system run more than one Nvidia graphics cards simultaneously for greater performance.

Nvidia has transferred all SLI implementation responsibilities to the game developer and game engine and won't release new SLI driver profiles for the RTX 20-series and older GPUs starting January 1.

"For GeForce RTX 3090 and future SLI-capable GPUs, SLI will only be supported when implemented natively within the game," Nvidia said.
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What does this mean for SLI? Nvidia hasn't done SLI any favors over the past several years. The GTX 900-series was the final architecture by Nvidia to fully support SLI in its entirety, specifically 3-way and 4-way SLI configurations.
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Now, with Ampere, Nvidia has limited SLI to the RTX 3090, which is poised to be one of if not the best graphics card on the market upon release. But there's good reason for this. Since its inception, SLI has been riddled with bugs, crashes and inconsistent frame times, resulting in choppy gameplay. Getting the tech working correctly requires a lot of optimization from the game developer and from Nvidia. Additionally, there isn't a large market of PC gamers running more than one graphics card in their PC.

With Nvidia dropping SLI support for the RTX 3080 and below, Nvidia can free up resources, allowing its driver teams to work on other things. You might get performance improvements due to low-level API support. Nvidia has stated that SLI's only purpose right now is to make the fastest gaming rigs in the world, and this is a good way to keep that going.

Quote:Buried in the bowels of the driver change-log is a big disclosure, that the RTX 30-series "Ampere" GPUs don't support SLI (as in implicit multi-GPU), only explicit multi-GPU through modern APIs such as DirectX 12 and Vulkan (if supported by the game). NVIDIA has already restricted the NVLink interface needed for SLI only to its topmost RTX 3090 SKU, so the lack of implicit multi-GPU effectively marks the end of SLI for future GPUs. That said, the technology itself is very much present on all GPUs that support it, provided games do.

Quote:Nvidia made this announcement in the release notes for Version 456.38 of its GeForce Game Ready Software. Beginning on January 1, 2021, no new implicit SLI profiles will be provided for any RTX 2XXX or earlier GPU. All GPU support for SLI going forward will be via explicit SLI, which is to say, the game will have to support the mode directly rather than implementing the mode in-driver.

There’s little reason to expect game developers to consider doing this, however. Of the various Ampere GPUs, only the RTX 3090 has the appropriate bridge connection points. Game developers aren’t likely to invest in optimizing for the tiny percentage of the market that buys such cards, and while they may implement explicit support in a few games going forward to serve existing SLI owners, I expect the feature to die now that Nvidia won’t be providing implicit driver updates any longer.

This will not affect any application that can run across multiple GPUs without depending on SLI, and the number of gamers likely to be impacted by these changes is small. The truth is, in the 10+ years that SLI has been available from AMD and Nvidia, it’s never really lived up to its promise. Performance gains have been weakening for years, and it’s not unusual to see people with SLI rigs complaining that neither of their GPUs is running at 100 percent.
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SLI also had to confront some intrinsic limits: Under the old, DX11-era model, GPU data in one card must be duplicated in the other. You might have two cards with 8GB of RAM each, but the total amount of memory in your graphics array was 2x8GB — not 16GB. DirectX 12 lifts this restriction, but that hasn’t been enough to drive much vendor interest in the feature.

Because DirectX 12 is a low-level API, Nvidia’s old mechanisms for enabling SLI performance in DX11 games can’t work the same way, and developers have had a limited appetite for implementing SLI in the first place. Things might have evolved in a different direction if SLI had become truly popular. In a world where consumers prefer playing with two lower-cost GPUs as opposed to a higher-cost model, we might have seen more of an effort to develop engines and rendering techniques specifically friendly to multi-GPU scaling. This did not happen.

It seems unlikely Nvidia will retain the feature indefinitely, and the RTX 3090 may be the last card to feature it, but the death of SLI isn’t really something to lament. The technology never caught on in-market the way it would have needed to in order to drive its own adoption and optimization. Nvidia’s support was typically better than AMD’s, but as someone who used SLI at several points, it was always tetchy.

The era of multi-GPU gaming has effectively come to an end — at least for now.