There’s a YouTube channel that planned to test Nvidia’s new GeForce RTX 4090 in a different way by pitting it against two RTX 3090s in SLI.  

Yes, it is true, SLI – Nvidia’s obsolete multi-GPU tech was managed to run by using some unknown SLI-enablement magic. So, the channel was able to run SLI very well in several DX11, DX12, and Vulkan titles, but the 3090s could not beat the RTX 4090. 

SLI has been unsupported for years and getting it to work with modern titles like DX12 and Vulkan would need unorthodox methods. It is still not known how the channel managed to enable SLI in most of the games tested especially the DX12 versions. But the results seem to be quite interesting. 

The said YouTube channel tested 9 games namely Spider-Man Remastered, Cyberpunk 2077, Watch Dogs Legion, Microsoft Flight Simulator 2020, Minecraft RTX, God of War, Witcher 3, Horizon Zero Dawn, and Read Dead Redemption 2. Testing was done at 4k resolution by using different quality settings and DLSS modes. 

In Spider-Man Remastered, with maxed-out settings, the RTX 3090s in SLI achieved 80-85 frames per second (fps) on average, whereas the RTX 4090 managed a higher 95 fps average. 

In Cyberpunk 2077, with maxed-out settings, the RTX 3090s in SLI got 50 fps while the RTX 4090 got almost 70 fps. 

In Watch Dogs: Legion, with maxed-out settings, the RTX 3090s in SLI averaged 73 fps and the RTX 4090 averaged 80 fps. It’s a little different though. 

The results were closer in Microsoft Flight Simulator with maxed-out settings. The RTX 3090s in SLI averaged 80 fps, whereas the RTX 4090 averaged 83-85 fps.  

In Minecraft RTX, with max settings, the RTX 3090s in SLI averaged 70 fps while the RTX 4090 achieved a little higher average of 75 fps. And in God of War at max settings, the RTX 3090s in SLI hit an average of 103 fps whereas the RTX 4090 gave a better performance with an average of 120 fps. 

For the rest of the titles too, RTX 4090 has been a better performer. 

With the exception of Cyberpunk 2077 results, the RTX 3090s in SLI were 8-15% slower than the RTX 4090. This is not bad at all for an SLI implementation and it is the only GPU configuration we have seen so far that can get close to the RTX 4090’s performance bracket.  

The 3090s in SLI setup was not used fully as the secondary 3090 maxed out at 45% utilization. This is a drawback on part of SLI setups, where bad optimization leads to less GPU utilization on the secondary card. So, if we could get at least close to 100% utilization on both GPUs, we would see the 3090s in SLI outperform the 4090 by a good margin. 

But the chances are less as Nvidia officially killed off SLI in the form of physical bridges with the RTX 40 series. SLI support has dwindled a lot over the past years it is presently only useful in synthetic benchmarks. 

There are ways of enabling SLI (unofficially) in games that do not support it. Though these results are unpredictable and usually result in system instability or severe micro-stuttering problems while gaming. 

There is still little hope for SLI, however. Multi-GPU workloads are common in the enterprise space, and Nvidia has multi-GPU technologies that do not need an NVLink or SLI bridge. 

As per gaming, modern APIs like DX12 and Vulkan has the capability to render frames to two different GPUs in tandem. So, multi-GPU tech might make its way back to the gaming space eventually.