How does "Fast sync" fit into this* (*Low latency mode) ?

agent_x007 wrote on 2025-10-14, 19:46:

How does "Fast sync" fit into this* (*Low latency mode) ?

No idea how those two work together, as I don't normally use Fast Sync. While I'm aware of its advantages, I don't like how it maxes out my GPU at 100% pretty much all the time.

For me personally, proper frame pacing is more important than having the lowest possible input lag. That's because I don't play competitive shooters, and I tend to use a controller more often than not. Maybe it's possible to achieve that with Fast Sync as well, not really sure. I haven't tested it a whole lot because of the aforementioned GPU utilization issue.

Fast sync was designed to always synchronize refresh rate of your monitor to latest frame that was rendered (combining "no tearing" of being Vsynced, with lowest possible input lag).
GPU utilization isn't an issue, because it's simply a byproduct of forcing GPU to render frames as fast as possible (to get the lowest possible input lag).
If you like to see less utilization (depending on circumstances), you can just limit your max. FPS to 120 or 90 (with 60/75Hz display).

agent_x007 wrote on 2025-10-14, 21:14:

If you like to see less utilization (depending on circumstances), you can just limit your max. FPS to 120 or 90 (with 60/75Hz display).

I tried this on my Ryzen 7 + RTX 3060 rig, and it is indeed working nicely. Using Fast Sync, while also limiting FPS to a multiple of the display's refresh rate, does seem to yield good results. For this purpose, I ran an older game (Deus Ex: Human Revolution) at 1080p with Fast Sync on, while keeping Nvidia's frame limiter at 120 FPS (since my TV runs at 60Hz). The controls felt very responsive, there was no screen tearing, and I got a perfectly flat line on the frametime graph. Also, due to the FPS limit, GPU utilization was fairly low.

Unfortunately, many older games (DX:HR included) exhibit issues when running above 60 FPS. I could limit the frame rate to that value, but I'm not sure if/how that would be different from using normal V-Sync. In any case, this is certainly an interesting approach.

P.S.

I also tried using Fast Sync without setting an FPS limit, but that made the frametime graph pretty wobbly, in addition to increasing GPU utilization.