ISSUE DESCRIPTION
Bug Report
MSFS 2024 – Severe MainThread Stutters in Cruise Flight Related to Terrain Pre-Caching (High/Ultra)
Hello everyone,
I would like to report a reproducible stuttering issue in MSFS 2024 that appears to be related to Terrain Pre-Caching and terrain data management, rather than hardware performance.
After extensive testing over the last weeks, I have been unable to identify any fault with my hardware, Windows installation or simulator installation. The issue appears to be reproducible and seems closely linked to Terrain Pre-Caching, terrain-heavy regions, and camera behaviour.
System Specifications
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CPU: AMD Ryzen 7 9800X3D (stock settings)
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CPU Clock in MSFS: ~5225 MHz
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GPU: NVIDIA RTX 5080 16 GB
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RAM: 64 GB DDR5 (2×32 GB) 6000 MHz CL30
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Storage: 2 TB NVMe SSD
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Operating System: Windows 11 (clean installation)
No overclocking, no undervolting, no Curve Optimizer, no PBO.
Main Symptom
The simulator generally performs very well with stable FPS.
However, during cruise flight I experience sudden MainThread frame-time spikes, resulting in visible micro-stutters despite FPS remaining relatively stable.
The issue occurs mainly in areas with a large amount of terrain data, for example:
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London
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Boston
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Washington
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Ireland during Atlantic crossings
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Other terrain-heavy regions
It occurs with every aircraft I have tested, including default aircraft and third-party aircraft.
Very Important Observation
One observation stands out:
When I keep the cockpit camera completely stationary for a longer period of time during cruise, the MainThread stutters become significantly more frequent.
As soon as I start moving the camera again, even slightly, the stuttering immediately becomes less frequent or temporarily disappears.
This behaviour is fully reproducible.
It almost seems as if moving the camera forces the simulator to refresh or reorganize terrain cache data, while leaving the camera stationary allows some terrain/background management process to accumulate until a periodic MainThread stall occurs.
Terrain Pre-Caching Behaviour
After many hours of testing, I found the following:
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Terrain Pre-Caching Ultra → severe cruise stutters
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Terrain Pre-Caching High → exactly the same behaviour
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Terrain Pre-Caching Medium → cruise stutters are mostly gone
Unfortunately, Medium introduces another problem:
Camera changes and panning become noticeably less smooth because terrain outside the current view has to be loaded again.
Therefore Medium is only a workaround, not a solution.
The fact that High and Ultra behave identically, while Medium almost eliminates the cruise stutters, strongly suggests an issue within Terrain Pre-Caching itself rather than a hardware limitation.
Developer Mode Performance Overlay
During normal flight:
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FPS around 60
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Graphics Queue approximately 14–15 ms
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MainThread typically around 13–15 ms
During the stutters:
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MainThread suddenly jumps to around 30–35 ms
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Graphics Queue remains relatively stable
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GPU is not overloaded
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VRAM usage is well below the 16 GB limit
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System RAM usage is normal
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“MarkersFailed” sometimes increases significantly
From the performance overlay it appears that the GPU is not the limiting factor during these stutters.
Instead, the MainThread seems to be periodically waiting for another subsystem.
Everything I Have Already Tested
The issue remains exactly the same after testing all of the following:
Simulator
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Complete MSFS 2024 reinstall
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Community folder empty (except testing some airport addons)
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Happens with every aircraft
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Happens regardless of departure airport
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Happens even away from addon airports
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Cabin and no-cabin versions tested
Windows
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Clean Windows 11 installation
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No background applications
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Background applications running
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Balanced power plan
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High Performance power plan
No difference.
Online Features
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Bing Data ON/OFF
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Photogrammetry ON/OFF
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Online Services OFF
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Live Weather OFF
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Live Traffic OFF
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Multiplayer OFF
No difference.
Graphics
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Frame Generation ON
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Frame Generation OFF
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TAA
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DLSS
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High and low Terrain LOD
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High and low Object LOD
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Terrain Vector Data Medium
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Different graphics presets
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Different FPS caps
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RTSS FPS limiter
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NVIDIA FPS limiter
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VSync combinations
No difference.
NVIDIA Driver
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Latest Game Ready driver
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Older Game Ready drivers
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G-Sync ON
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G-Sync OFF
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Fixed Refresh
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HDMI instead of DisplayPort
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NVIDIA Low Latency Mode OFF
No difference.
Hardware / BIOS
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ReBAR ON/OFF
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HAGS ON/OFF
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Rolling Cache ON/OFF
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Rolling Cache deleted
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CPU running completely stock
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BIOS defaults
No difference.
The only remaining test I have not yet performed is disabling SMT.
Why I Believe This Is Not A Hardware Issue
The hardware should easily be capable of running MSFS 2024 smoothly:
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Ryzen 9800X3D
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RTX 5080
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64 GB DDR5 6000 CL30
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Fast NVMe SSD
The issue also persists after:
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Clean Windows installation
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Clean simulator installation
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Multiple NVIDIA drivers
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Online services disabled
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Frame Generation disabled
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Different FPS limiters
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Different monitor configurations
Because the problem is specifically linked to Terrain Pre-Caching and terrain-heavy areas, I do not believe this is a conventional CPU or GPU bottleneck.
Similar Reports / Related Threads
While investigating this issue, I found several reports that appear to describe the same or a very similar problem. Although not every report matches my symptoms exactly, there is a recurring pattern involving MainThread spikes, Terrain Pre-Caching, terrain-heavy areas, and camera-related stutters.
1. Off Screen Terrain Pre-Caching causes intermittent spikes and horrible stutters (MainThread)
This is by far the closest report to my issue. Users describe intermittent MainThread spikes directly linked to Off Screen Terrain Pre-Caching, even on high-end hardware.
2. Stuttering / Micro-freezes even with high FPS
Several users report severe micro-stutters despite high FPS, with MainThread spikes occurring mainly during flight rather than because of GPU limitations.
https://forums.flightsimulator.com/t/stuttering-micro-freezes-even-with-high-fps-need-help/708216
3. Persistent stutters and flight interruptions on high-end PCs
This discussion contains multiple reports of periodic MainThread spikes and frame-time issues that remain even after disabling Frame Generation.
4. Camera panning stutters related to Terrain Pre-Caching
Several users describe stutters that change depending on camera movement. While my issue is the opposite (stutters increase when the camera remains still and decrease when moving it), it still suggests that Terrain Pre-Caching and camera behaviour are closely related.
https://forums.flightsimulator.com/t/stutter-when-panning-camera-in-external-view-in-su-5-1/765935
5. Off Screen Terrain Pre-Caching discussion (MSFS 2020)
Although this thread is from MSFS 2020, it already discusses MainThread stutters caused by Off Screen Terrain Pre-Caching.
https://forums.flightsimulator.com/t/off-screen-terrain-pre-caching-stutter/493670
6. LOSS – Lexicon of Sim Stutters
This community investigation classifies different kinds of simulator stutters. The section regarding Photogrammetry Mapping Stutter resembles what happens in terrain-heavy regions.
https://forums.flightsimulator.com/t/loss-the-lexicon-of-sim-stutters/654029
7. Micro stutters and performance degradation during flights
Users report that the simulator becomes less smooth during longer flights despite GPU usage remaining normal.
https://forums.flightsimulator.com/t/micro-stutters-and-performance-degradation-on-flights/680659
8. Rolling Cache causing periodic stutters
Some users observed periodic stutters related to terrain cache management. Rolling Cache ON or OFF makes no difference in my case, but the discussion may still point towards a broader terrain management issue.
Common Pattern
Across these reports, several recurring observations appear:
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MainThread spikes despite high FPS
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GPU is not fully utilized during the stutters
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Most noticeable in terrain-heavy or photogrammetry-heavy regions
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Closely related to Terrain Pre-Caching or terrain streaming
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High-end hardware does not prevent the issue
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Camera movement appears to influence stutter frequency
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Lowering Terrain Pre-Caching often reduces cruise stutters but increases view-change stutters
Taken together, these reports suggest that the issue may originate from the simulator’s terrain cache management, off-screen terrain pre-caching, terrain worker synchronization, or terrain residency system, rather than insufficient hardware performance.
Possible Cause
Based on all testing, my current suspicion is that the issue is related to one of the following engine systems:
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Off-screen Terrain Pre-Caching
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Terrain tile residency management
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Terrain worker thread synchronization
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Terrain cache eviction
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CPU-side terrain decompression
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Terrain object submission
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Background terrain management periodically blocking the MainThread
The camera behaviour is particularly interesting.
Normally, one would expect fewer updates while the camera remains stationary.
Instead, the opposite happens:
The longer the cockpit camera remains completely still, the more frequent the MainThread stutters become.
Moving the camera again immediately reduces the stuttering.
Combined with the High/Ultra Terrain Pre-Caching behaviour, this strongly suggests an issue within the simulator’s terrain cache management or terrain worker synchronization rather than a conventional CPU or GPU performance bottleneck.
Current Workaround
The only workaround I have found is:
Terrain Pre-Caching = Medium
This almost eliminates the cruise stutters.
Unfortunately, it also causes noticeably more terrain loading and stuttering whenever changing camera views or panning around the cockpit.
Therefore this is only a compromise rather than a real solution.
Request
Could Asobo please investigate the Terrain Pre-Caching system, especially the behaviour of the High and Ultra settings during cruise flight?
The issue appears to be reproducible on high-end hardware and seems strongly connected to terrain-heavy regions, camera behaviour and Terrain Pre-Caching, rather than traditional CPU or GPU limitations.
If any developers or other users are able to reproduce these findings, I would be happy to provide additional performance overlay screenshots, recordings, or perform further testing if required.
Testflight i use as a benchmark
Below a link with an Autosave File for the INIBuilds A350 I use as a Benchmark because this addon is very performance heavy.
The flight goes from France LFPG over UK NW over Ireland to the Atlantic Ocean.
This is the route where the stutters are most pronounced.
Put it into :
C:\Users\Username\AppData\Local\Packages\Microsoft.Limitless_8wekyb3d8bbwe\LocalState\WASM\MSFS2024\inibuilds-aircraft-a350\work\autosaves
Load the file via the Autosave feature of the plane in the EFB
Its the same with any other plane if you try the route i described above.
