Some questions about Pendulum Demo

[matrox-40]

Hello.
This qestion was born because I'm searching how to get back smooth gameplay in iRacing, which in past was supersmooth for me and over time, as game gets updated, windows, drivers, everything changing...it became over time stutter fest and I cannot figure it out. Just in short words I know my platform can keep ideally smooth other titles (7800X3D & 4090). I have several monitors but this subject relates Dell G2724D. I'm testing this monitor, wich is max 165Hz, windows reporting VRR capability 49-165Hz.

I decided to test a bit via Pendulum Demo and I have found inconsistent behavior. It shows stutters, even though I can see monitor Hz fluctuation in menu, G-Sync indicator ON. Just close\open again Pendulum and its all butter smooth. So it seems launch-to-launch different behavior. Rarely, but also happened, cannot even click on G-sync square in Pendulum, it kicks me off to VSYNC or NO-VSYNC, like it cannot activate G-sync. So in this scenario I dont have G-sync indicator and also Hz is not changing in menu - image of course is stuttering\tearing.

In the end I'm aware this is "adaptive sync" monitor, so no guarantee. So is this a way that non-hardware chip-G-sync monitors behave ?

But then after some time spend with Pendulum:

- when I launch it, it starts somewhere around 120FPS for several seconds
- then I see it lowers FPS and it stabilizes somewhere at around 35-45FPS

starts 120 FPS

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Quesions are:
- whatever FPS is there (or I manually select by sliders), GPU usage is always 100%. I would be afraid, that with such constant max GPU usage, only this may cause \ add to stutter, and for me Pendulum Demo was to ensure my platform can deliver smooth, but not eventually at 100% GPU usage. Why is this designed this way ?

- when Pendulum goes to quite low FPS and stays like that by default, I see that Hz fluctuating in my monitor is double the value od "animation FPS". As for many monitors low VRR treshold is somewhere at around 50Hz, why Pendulum goes to level, that may exceed many monitors VRR range ? Is monitor doing some multiplication of frames or so? In fact, this 35FPS pendulum (and monitor shows varying around 70Hz) is not sufficent with FPS, but I wouldn't say its stuttery, It still seems like synchronization is active

- even though I set manually for example low FPS=70 and high=120, which for my PC and expectations is desired range, I see stutters. Next launch - ideally smooth. Tested on three monitors (I have tripple setup for iRacing), different DP cables, so it seems to be structural problem?

Regards,

[Gias]

Is monitor doing some multiplication of frames or so? In fact, this 35FPS pendulum (and monitor shows varying around 70Hz)

yep nvidia geforce display drivers can duplicate / multiply frames below the minimum refresh rate.

https://nvidia.custhelp.com/app/answers ... compatible

that's typically known as LFC (low framerate compensation)

your 35fps resulting in the monitor showing 70hz looks like LFC at work to me

(technically the display's max refresh rate is not changed from its max. gsync uses the display's full refresh/scanout speed and then basically waits if the game's fps/frametime is lower, and so vrr also uses qft / quick frame transport).

as for your game and its stutters, that can come from different things...

gsync is basically for tackling tearing without incurring the typical latency penalty from vsync and for removing judder that you could have from an fps / refresh mismatch; games could still stutter for various reasons even if you had very consistent frame pacing with a good fps limiter... since frames could still be rendered by the game with screwed timings, the game's physics may be simulated with wrong or improper timings, and gpu rendering as well as display time can also be factors that'd affect animation and perceived smoothness.

anyway, are you actually playing the game in a window spanning 3 displays ? that normally results in a composed flip presentation, which can hurt performance, results in higher latency, and would break gsync

gsync could work with games using a composed flip presentation with the "enable for windowed and full screen mode" option from the nvidia control panel, but that option in practice may not work great since it may not sync vrr properly to the game and vrr may sync to other stuff you may not want it syncing to...

ideally you'd set gsync to the option that says "enable for full screen mode" in the nvidia control panel and then gsync would work properly if your game is using legacy flip or independent flip for presentation. i'd normally also use an fps limiter from special k or from rivatuner statistics server to cap fps to something i can more consistently maintain.

another thing that can help some games is enabling reflex boost or setting the "power management mode" option in the nvidia control panel to "prefer maximum performance." that can prevent gpu frequency scaling and it keeps gpu clocks high (though i'd generally only suggest enabling that for a game driver profile; not in the global driver profile).

you can check a game's presentation model using intel's presentmon, or with special k, or with rivatuner statistics server (though i don't think special k would work with iracing specifically since apparently that game uses easy-anti-cheat, which blocks sk...)