Up to 64% Performance Penalty for Gamers using G-Sync, SLI Together

Nvidia SLI for connecting two GeForce GTX cards

Nvidia’s G-Sync and SLI are both useful technologies, especially for enthusiasts trying to build a high-end PC. But it seems that when the two are combined to extract the maximum performance out of Nvidia’s ecosystem, users could experience an FPS drop as high as 64%.

That’s the issue raised by fans on the Nvidia forums. They noticed that enabling G-Sync degrades performance across the board with Pascal GPUs. One user ‘octiceps’ even posted benchmark results comparing G-Sync On to G-Sync off. He tested five different games running in SLI at 1080p, and here is what that looks like:

 G-Sync OffG-Sync On
Battlefield 1163 FPS116 FPS
Rising Storm 2206 FPS75 FPS
Deus Ex Mankind Divided152 FPS91 FPS
Sleeping Dogs Definitive Edition143 FPS113 FPS
Witcher 398 FPS98 FPS

This is not the first time such complaints have emerged online, but they date back since Nvidia’s Pascal GPUs launched. That said, early reports suggest that Nvidia has fixed this issue with the Turing-based 20 Series GPUs.

So what exactly is the problem here? We’re not sure, but many speculate that timing could be the root cause of the issue.

For those who don’t know, SLI is Nvidia’s technology, which lets gamers use more than one GPU to render a scene at the same time. G-Sync, on the other hand, is a technology which syncs a monitor with the refresh rate of the GPU. That smoothes frame rates compared with standard V-Sync, thus helps eliminate screen tearing and input lag.

Now moving data from one GPU to another while keeping the GPU and monitor in sync takes time. So timing is a major implication when using both G-Sync and SLI.

Nvidia G-Sync, SLI for performance penalty

ExtremeTech decided to explore this issue in-depth. They set up a system with dual GTX 1080s and an Acer XB280HK G-Sync monitor. The monitor is 4K capable, which is handy considering many SLI users buy into the technology to achieve 60FPS at UltraHD resolution. The performance however didn’t exceed 60FPS as to stay within the monitor’s G-Sync range.

They tested three games in total, all running in 4K. Of those, Far Cry 5 showed a 16% FPS drop when activating G-Sync and Hitman suffered a 20% drop. The third title, Deus Ex: Mankind Divided, showed a 10% FPS drop with G-Sync enabled, but only in DX11 mode; the gap vanished when switched to DX12.

The analysis concludes that “the issue is real and that the performance gaps could be as large as Nvidia users say, particularly if they continue to worsen as frame rate increases.” It further states that Nvidia “owes its customers an explanation for this behavior” as the company has repeatedly denied any claims of performance penalty tied to using SLI and G-Sync.