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Re: Why do Pro gamers not use G-Sync?

PostPosted: 26 Apr 2017, 14:08
by RealNC
You also need to consider inconsistencies in mouse input handling between different refresh rates and different amounts of CPU and/or GPU load, and also GPU drivers behaving differently when the GPU is being maxed out. Overwatch had lots of people reporting input lag increase at high frame rates. Blizzard responded at some point (but the post has been removed now; I think they either purge or move old threads), but the Internet Archive still has it:

Thanks for all the feedback. I can give you a little bit more information about the details of input lag.
We use only unadjusted raw input for our input handling (except when in the UI) as is common for FPS's. We also do a few other things to try to minimize input lag (sample input at the latest possible moment, minimize allowable buffered frames in the driver, etc).
However, we have noticed that if the GPU gets bogged down, input lag will be a little bit worse because the driver will start to buffer a frame and there can be a frame buffered in our game (we have a multi-threaded renderer that has a frame in submission to the GPU while we simulate the next frame). In those cases if you want to prefer less input lag over visual quality you can reduce your graphics detail settings to ensure you get the quickest path from sampled input to result on screen.

Lowering the details in Overwatch resulted in hitting the internal FPS cap of the game, so GPU load was reduced.

I think it's still beneficial to cap your frame rate even in games where you get high frame rates. At very high frame rates (400FPS and up) it doesn't make a difference. 1 frame at 400FPS is not worth mentioning. But 1 frame at 200FPS is somewhat significant. If your PC maxes out at less than 200FPS and even though your minimal FPS is still in that ballbark (160-ish for example), then a cap might actually improve input lag.

Re: Why do Pro gamers not use G-Sync?

PostPosted: 26 Apr 2017, 19:46
by Chief Blur Buster
Caps can easily improve lag for GSYNC and VSYNC ON situations

However, caps improving VSYNC OFF lag is not common -- and if so, I think it is hugely dependant on the game. Uncapped framerates will often have less input lag during VSYNC OFF situations.

A major use of a cap at high framerate such as fps_max 300 and fps_max 500 is to help framerates stay more consistent, since there's a latency yo-yo effect from framerates going all over the place in uncapped-framerate situations. Yo-Yoing from 250fps to 1000fps and back is a 3ms frametime-induced lag difference, big enough to throw off precision flick aiming in low-lag-jitter situations (Quake, CS:GO). And historically, there are situations -- multithreaded games -- where uncapped framerates may cause other threads to starve (e.g. input reads getting slowed down, etc). But in the era of quad-core i7, this is far less likely to happen.

Re: Why do Pro gamers not use G-Sync?

PostPosted: 26 Apr 2017, 20:43
by RealNC
Well, I'm going from what Blizzard said here, that maxing out the GPU made the driver start buffering a frame.