27GN850-B G-Sync Compatible Stutter

Talk about NVIDIA G-SYNC, a variable refresh rate (VRR) technology. G-SYNC eliminates stutters, tearing, and reduces input lag. List of G-SYNC Monitors.
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nintendo424
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27GN850-B G-Sync Compatible Stutter

Post by nintendo424 » 20 Jul 2021, 10:25

Hi everyone, I picked up an LG 27GN850-B (I believe the successor to the 27GL850) back in September 2020, and ever since I got it, I've noticed stutter in games.
I previously had an AOC G2460PG which has a G-Sync module, and it was wonderful. I decided to go with this monitor because of it being IPS and being G-Sync compatible, and so I gave it a shot.

I have configured my monitor using the G-Sync 101 guide, G-Sync ON, V-Sync ON, and using RTSS to limit the fps to 141 since it's a 144hz monitor. I've also used NULL and the NVCP limiter too, no difference there.

I'm running an ASUS Strix 1080ti and an Intel i9-9900k, so performance isn't the issue as far as bottle necks that I've been able to find.

The stutters happen in pretty much every game I've tried, Rocket League, Apex Legends, Final Fantasy XIV, and a couple others I can't remember at the moment.
I've found that removing G-Sync from the equation and leaving v-sync ON runs perfectly smooth. Also disabling g-sync and v-sync, I get well over 250fps in Rocket League with little frame time variation.

The monitor itself (or at least LFC) seems to be the culprit, as watching the OSD monitor shows that even when maintaining a stable 141hz, the monitor's frame rate fluctuates between 135 and 144, not really landing on 144 and mostly staying right at 144.

Unfortunately the 27GN850-B has no firmware updates, nor a USB input to install them with, so I feel at a loss at the moment.
Does anyone have any suggestions as to what to try?

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RealNC
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Re: 27GN850-B G-Sync Compatible Stutter

Post by RealNC » 20 Jul 2021, 11:45

As a test, what happens if you cap to 120FPS?
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nintendo424
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Re: 27GN850-B G-Sync Compatible Stutter

Post by nintendo424 » 20 Jul 2021, 12:15

The stutters decrease, but they are definitely still noticeable. I can also see the monitor OSD is fluctuating wildly. For example, in Ni No Kuni Wrath of the White Witch, with a 120fps limit in NVCP, the monitor's OSD goes between 112 and 144 constantly. In the menu, with nothing going on, the framerate graph from RTSS is 120 HPS, 8.3 ms without changing, but the OSD goes between 117, 120, 133, 144 constantly without any certain discernable pattern. I could post a video link but I don't think I can post external links.

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Re: 27GN850-B G-Sync Compatible Stutter

Post by Chief Blur Buster » 23 Jul 2021, 18:33

That's strange. I wonder if this is a driver bug.

(In FreeSync, Drivers operates LFC in a software-timed manner, not the monitor.)

It is currently well-known that NVIDIA's implementation of FreeSync is worse than AMD's implementation of FreeSync, and NVIDIA's implementation of native chipped G-SYNC.

It could be the monitor issue, but the thing is stutters often stop when switching from an NVIDIA card to AMD card on the same FreeSync monitor. So, we cannot always blame the monitor;

Any attempts at a fully clean driver uninstall and reinstall?
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jorimt
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Re: 27GN850-B G-Sync Compatible Stutter

Post by jorimt » 25 Jul 2021, 10:57

nintendo424 wrote:
20 Jul 2021, 10:25
The monitor itself (or at least LFC) seems to be the culprit, as watching the OSD monitor shows that even when maintaining a stable 141hz, the monitor's frame rate fluctuates between 135 and 144, not really landing on 144 and mostly staying right at 144.
For one, the built-in VRR refresh rate meter on a FreeSync display running in G-SYNC Compatible mode, at least from other user reports I've seen, is completely unreliable; I don't doubt you're experiencing stutter in VRR mode, but the refresh rate meter probably can't be relied on to accurately reflect that. It's going to rapidly jump around, stutter or no stutter.

Have you tried this RTSS add-on overlay instead? It should give you a more reliable VRR readout:
https://forums.guru3d.com/threads/does- ... st-5823497

That said, while this could indeed be LFC/driver-related stutter (as the Chief suggested), it's possible you could be experiencing frame skipping, as other G-SYNC Compatible displays have suffered this in the past (even my LG CX did at one point in time before a firmware update). Have you tested for that in G-SYNC Compatible mode?
https://www.testufo.com/frameskipping

If it is frame skipping, it would likely be a timing issue with the out-of-box VRR resolution preset, which could potentially be corrected by a custom res via CRU, but it would be specific to your model (perhaps even to the unit itself).
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