[Thread Superseded] G-Sync 101 w/Chart (WIP)

[jorimt]

Preliminary input latency tests have been posted to the OP. More to come, stay tuned...

[flagbender]

Thanks for doing these tests

I just got a PG279Q "overclockable" monitor. Generally you don't want to play with that, but in light of these tests, I think conceptually it sounds like a good idea to overclock the monitor to about 150hz just to avoid even the remote possibility of vsync activating with a high-ish cap, right? You could even maybe try a 144fps instead of an 142fps cap, and then the monitor would be staying at its actual native refresh rate much of the time instead of almost never.

Let me know what you think?

[lexlazootin]

PG279Q 'overclocks' to 165hz out of the box. just use that and cap below it.

I would recommend see if you could even push it farther.

[flagbender]

I'm not generally interested in overclocking because it's been shown to cause slow response times at the non-native (overclocked) refresh rates. But I figured it could be useful for Gsync just to overclock a little bit and then cap framerate at 144 (so your monitor is actually at its best refresh rate mostly) without triggering vsync, because the new vsync trigger point would be the overclocked refresh rate.

[jorimt]

Thanks for doing these tests

I just got a PG279Q "overclockable" monitor. Generally you don't want to play with that, but in light of these tests, I think conceptually it sounds like a good idea to overclock the monitor to about 150hz just to avoid even the remote possibility of vsync activating with a high-ish cap, right? You could even maybe try a 144fps instead of an 142fps cap, and then the monitor would be staying at its actual native refresh rate much of the time instead of almost never.

Let me know what you think?

Your monitor, your preference, your prerogative.

That said, starting at around 85 Hz, perceptive gains for the average user begins to decrease over, say, the initial 60 Hz, when moving to 100 Hz or 120 Hz. The perceptive difference between 120 Hz and 144 Hz, while appreciable to the more trained eye, is even less. At 144 Hz, the difference between 142 fps and 144 fps is virtually undetectable (compared to 58 fps vs 60 fps, which is much more appreciable at 60 Hz), and since the frames are still physically scanning in at the display's maximum refresh (144 Hz = 6.9ms frame completion time), in my opinion, it isn't worth overclocking to 150 Hz just to maintain a 144 fps cap.

I'm not generally interested in overclocking because it's been shown to cause slow response times at the non-native (overclocked) refresh rates. But I figured it could be useful for Gsync just to overclock a little bit and then cap framerate at 144 (so your monitor is actually at its best refresh rate mostly) without triggering vsync, because the new vsync trigger point would be the overclocked refresh rate.

Correct, there is no guarantee the G2G times/overdrive implementation will improve with an overclock, and in fact, they may degrade on certain high refresh monitors, a reason why I also opt for my display's native 144 Hz over the overclock. And in my preliminary 165 Hz input latency tests (not yet published), input latency was only reduce 1ms (or less) on average over 144 Hz. Always nice to have the option though.

[flagbender]

Firstly, I think the main thing was that it would guarantee that you wouldn't ever go over the vsync limit even if you were off by a few frames.

Also what you're saying is true, and I can appreciate 2-3 fps is probably undetectable. But.. if the option is there to do it for free, then why not I suppose? Especially since the option is worthless for anything else.

[jorimt]

Firstly, I think the main thing was that it would guarantee that you wouldn't ever go over the vsync limit even if you were off by a few frames.

Also what you're saying is true, and I can appreciate 2-3 fps is probably undetectable. But.. if the option is there to do it for free, then why not I suppose? Especially since the option is worthless for anything else.

Forgive the lack of a direct response to your last reply. I think you are misunderstanding a key point here. The triggering of v-sync behavior with G-Sync enabled, and the fps limit required to avoid it, is exclusive to the current native refresh rate of the panel.

Once you switch the display from 144 Hz to 150 Hz, the display, now running at 150 Hz, is no longer linked or constrained by the fps limit required to stay under the G-Sync ceiling at 144 Hz. Instead, it now requires its own limit, which would be about 148 fps.

With a 144 fps limit at 150 Hz, you're simply robbing yourself of four frames.

I hope that's clearer.

[Bouttime]

This is a fantastic post and something that Nvidia should have put out. Providing the option to disable V-Sync with G-Sync enabled has really confused a lot of people....including me. This post has provided some clarity.

But I have a problem specifically with World of tanks on my Asus ROG G752VT gaming laptop which has a GTX 970m GPU.

Strangely, with G-Sync on and with V-Sync off (in Nvidia Control Panel and in-game), my FPS do not exceed the max refresh rate of the monitor which is 75hz. In fact what they do is drop to between 50-60 FPS and I get terrible stutter.

If I turn V-Sync back on my FPS go back up to the displays max of 75 and it's smooth with no stutter and also no perceived latency/lag.

Now on my Desktop I have a ROG 144hz 1440 display and GTX 970 GPU. I have G-Sync on and V-Sync off and gameplay is smooth. My FPS vary between 80 and the games max of 127. Now I would not expect to see tearing as the FPS are so high and the monitors max refresh rate is not being exceeded. But I do not get any stutter either. Yet with my laptop I do!?

The Preferred Refresh Rate option is not in Nvidia Control Panel for my laptop, but it is for my desktop. So I installed Nvidia Inspector on the laptop and the option is there and it is defaulted to let the game control it. If I change it to 'Maximum' then the stutter almost disappears and the FPS will also now exceed the 75 max refresh rate (when V-Sync is off) but I then obviously get tearing.

For info, on my 144hz G-Sync desktop monitor and GTX 970 GPU the Preferred Refresh Rate option is there in NCP and it defaults to 'highest' which is the opposite to my 75hz laptop screen. But I still max out at ~127 FPS which I believe is the maximum WoT can push out. I have V-Sync off in-game and in Nvidia Control Panel and the game is smooth as butter.

My conclusion is that quite possibly World of Tanks is struggling to cap the FPS at 75 without using V-Sync. I previously believed that we no longer needed V-Sync when G-Sync is running but this post (and one or two others) has made me realise that having them both on is how Nvidia intended it to work. They only introduced the option of turning it off for those playing games requiring extremely high FPS. Most people now seem to believe that V-Sync should otherwise be turned off due to an increase in input lag/latency, not realising of course that as long as FPS are within the G-Sync range then even with V-Sync selected on it isn't actually active anyway.

So as it turns out I've been on a bit of a wild goose chase trying to find out a way to be able to turn off V-sync and not get stutter. I'll just leave it on.

[Sparky]

G-sync can't stop the game engine from stuttering, it can just keep the interface between the GPU and monitor from causing stuttering. Maybe you can turn down settings, maybe you can add in some buffering to get more consistent frame interval at the expense of more input lag.

[Bouttime]

G-sync can't stop the game engine from stuttering, it can just keep the interface between the GPU and monitor from causing stuttering. Maybe you can turn down settings, maybe you can add in some buffering to get more consistent frame interval at the expense of more input lag.

The thing is with G-Sync and V-Sync both on, my FPS are averaging between 65-75 FPS so the GPU can handle the graphics settings fine. V-Sync is stopping the FPS from peaking higher but I have no need for higher FPS on my laptop. I prefer the FPS to be fairly constant and I don't want to see tearing.

But I'd read that V-Sync should be turned off to reduce latency/lag which is what started this whole thing for me. So what is strange is that with G-Sync on and V-Sync off the FPS goes down to 50-60 FPS and the game stutters badly like it would if my GPU couldn't handle the graphics settings. It's the only game that does this. I'll just leave V-sync on and be done with it.