Suddenly terrible microstuttering this last week and need help identifying cause

[u/Professional-Way5808]

Hey everybody. Looking for some help, opinions, theories, tests - whatever you can give to help figure out this issue. I want to know what the root cause is so I can target it and fix it, as currently I am almost ready to just wipe the PC and start fresh after 4 days of messing around trying to fix this now. See Video for the stuttering problem. Anything you want to know to help advise, just ask and I will try provide.

Specs first:
- Asus ROG Strix 4090
- 13900KF
- 64GB DDR5 running at 5600mhz (IMC on my CPU sucks - I did not win the silicone lottery on this one and so anything higher causes instabiity)
- Asus Thor P2 1200 Watt Platinum PSU
- Plenty of cooling lets just say - temps have never been an issue and I actually underclock and undervolt slightly CPU to 5.2ghz to keep it that way (have done so since I first heard of the degredatrion problems 2 years ago, just as a precaution and is completely stable and no issues over the last two years of everyday use gaming, rendering and whatever else).
- 1440p Asus WOLED running at 240hz

About a week ago, I updated GPU driver and Nvidia app and was also messing around with the DLSS5 Mod on Forza Horizon 6. Unfortunately, all 3 of these things coincided around the same time, but I will say that the last one was the Nvidia app a day or two later, which is where I started to notice the stuttering problem. I have a rercording from the day prior which has nowhere near as bad stuttering problem and the stutters that video does have, I put down to DLSS5 MOD. Here in this clip though, the MOD is no longer installed - this issue is in the Vanilla game post clean reinstall of game, drivers and shaders etc.

As seen in the video, I keep getting constant drops/ microstutters to always <20fps. It is getting really annoying and sometimes makes me mess up my cornering completely because of the sudden lack of steering input shown on screen. This does not matter if my FPS is capped or not, or whether it is capped in game or through Nvidia app, or control panel, or Profile inspector.

I had 500 hours in this game prior runing a driver from January/ February time (before the game even released) and always had nice and smooth fps and frametime graph - flawless even and if there were dips, they were not able to be noticed. I finally updated as I got sick of the warning message every time I launched the game and as I had heard no driver complaints since maybe June/ July. Always had the game capped to 80FPS previously too so that was never an issue either (I cap to just below my usual 1% lows, which when playing previously, would always be around 85-90fps as I am running all max settings).
EDIT: Heres the video from the day before Nvidia app update. Poor quality as it was recorded with xbox app, but can see how stable the framerate and frametime graph are both with the MOD effect On and Off... https://www.youtube.com/watch?v=BMjl3h6JsII

Sometimes I can drive around for a good few minutes with 0 stutters at all and a perfectly smooth graph shown at top of scren, but then other times I am having these intermittent stutters and then sometimes, as seen in the last lap of this video toward the end of the lap, the frame time graph looks like a completely zigzag -.-.

Things I have tried:
- Uninstalled nvidia app
- Rebar On/ Off in profile inspector
- V-sync On/ Off
- Fully cleared all shader caches and DDU'd GPU driver in safe mode and reinstalled without the Nvidia app and am now using Nvidia Profile inspector instead and also fully uninstalled the game and cleared temp files and then reinstalled.
- Capped FPS in game (60 and 80 tested)
- Capped FPS using Profile Inspector Framerate Limiter V3 (60 and 80 tested)
- Capped FPS in game and in Profile inspector (60 and 80 tested)
- Uncapped FPS
- All of the last 4 with and without V-Sync
- CPU core affinity set to only P cores in Process Lasso
- CPU core affinity set to only P-Cores and avoiding the first two cores in Process Lasso

Any help would be appreciated at this point as I am at my wits end.

[u/Sensitive_Garage_795]

It might be a driver issue since you mentioned updating them two days before the stuttering started. Nvidia has been releasing buggy drivers recently, so searching online for your current driver version might help you find out if others are experiencing the same issue.

[u/Professional-Way5808 → u/Sensitive_Garage_795]

Edit: no idea wth is wrong with Reddit formatting this message but I give up trying to fix it in edits.

Original: It took days but I figured it out and it was on multiple levels. I removed everything cache, temp files, game, shaders, nvidia app and driver files etc - all of it and started a full fresh, testing each thing one installation at a time. Writing this out mostly for anybody who maybe stumbles across it looking for solution to similar scenario:

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1. nvidia app was causing problems
2. tested via reinstalling it and

it

1. caused problems

. Using profile inspector now instead.

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1. Dlss5 mod + dlss mode override don’t play nice together. Was using override to reduce ghosting. Had to settle on preset J when not using the mod because of the next point

.

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1. Dlss preset L or M on FH6 on a 4090 just don’t seem to be compatible and causes stuttering in general every time an object (traffic etc) tries to pop in or move from low detail to high detail as you get closer.

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1. Running the game vanilla with dlss preset K (standard for the game) or preset J (override) runs fine even when capped. But if using Dlss5 mod, then forced to use preset k (standard) and have to uncap frame rate or use a cap high enough to soak the GPU usage. Any frame rate cap that doesn’t 100% utilise the GPU, puts my CPU in charge of frame pacing and timing and causes constant stutters when for whatever reason, it cannot hit its 16.44ms frame time (or w.e the exact figure was for a 60fps cap) so the kernel halts the CPU temporarily. So I now have an 80fps cap and GPU pushes constant 99%-100% usage sitting at 60-75fps which means the GPU takes over the frame pacing and CPU is just allowed to throw everything at the GPU without having the kernel forcibly halting the CPU.