After 5 minutes, FPS drops from 70 to 10 fps

First time writing here. This is the same issue as After playing a few hours, FPS drops from 40 to 5FPS - #34 by tjsasakifln except my setup is less than minimum requirements and the issue affects me after flying for only 5 minutes.

Sabertooth P67 (10 years old I know, LOL).
i7 2600K, 16 GB RAM.
GeForce GTX 960, 2 GB VRAM.
250 GB SSD

So I realize that this doesn’t meet minimum requirements but I feel I should write about it anyway.

I’ve disabled traffic and set general rendering to the lowest settings (600x400). I fly out of a small airport north of Toronto and travel to a small airport further north of Toronto (so no cityscapes).

So initially flying is fine, but after 5 minutes, it grinds to a halt (10fps in cockpit view flying cessna 152). If I change camera to external view, I get 70fps again. If I change camera to external view (just behind the tail) and disable HUD I get 10fps (so I can’t fly, in other words).

Monitoring my CPU/GPU, whenever I’m in cockpit view, and my framerate goes to 10fps, the GPU goes down almost to nothing. Whenever I change back to external view the GPU spikes again to 90%. So the bottleneck appears to be the CPU (it’s feeding the GPU in external view, but not in cockpit view).

So I was thinking, what’s the difference between the two external views I mentioned? I believe one is called drone camera view. That is the good one. If I try to move the yoke, I’m not sure if I have control of the plane in drone camera view?

Anyway, in developer mode, displaying fps, I see “Limited by MainThread”, and I see response time for MainThread to as much as 700ms (when framerate goes down to 10fps).

So I’m considering buying either a new PC (to play MSFS 2020) or maybe I should try MSFSX instead? I just think it’s weird that it runs fine for 5 min. before it significantly slows down.

It’s your videocard, it only has 2 gig of vram so thats why it spikes to 90%.

Although you are low on vram they are reports of this happening even on the 30series cards.
My 2060super is suffering with this sometimes and in my case using 6gb out of the 8gb.
Sounds similar to this Long freezes after su5

When the framerate drops to 10fps, the GPU falls to 10% utilization. This happens in cockpit view.
But when I’m in external view, framerate rises to 70fps and GPU is at 90%. But unfortunately I can’t fly the plane in the external view.

It doesn’t seem to be a rendering problem (i.e. GPU), it looks like CPU is the bottleneck (“Limited by MainThread”).

I agree, I’m reading quite a few incidences, and they all sound similar. If even more powerful systems (than mine) exhibit similar symptoms, then buying a new system may not solve the problem.

Seeing your videocard is below the minimum system requirements, it will solve your problem. Your card can’t handle the game so the CPU tries to keep up, hence the “limited by Mainthread” warning.

Thanks for your reply. I’ll look into upgrading.

You are probably looking at full new pc, as when you now get a brand new powerful GPU, your CPU probably will be bottlenecking your new GPU as it’s pretty old already. There also is a memory leak right now in the game that will be fixed with the upcoming hotfix today.

I had the same experience as the OP.

Beginning of a flight, GPU utilization 100%, FPS around 120 FPS. 10 hours into the flight, GPU utilization is in the teens, and FPS around 20. Checked Task Manager and no major processes other than MSFS are running. CPU utilization is always pretty low. I’m not sure about the temps, I will test again and monitor.

Seems like a memory leak?

My specs:

i9-9900
RTX 3080
32GB RAM

I have the same problem…

FPS dropped from mid 40s to 10, watched it slowly descend just sitting at the airport or flying… switch aircraft and no probs… just that C152… Only took 3-5min for it the drop.
Had a similar problem where if I flew over the airport scenery area FPS would drop the same until i flew out of that section… Sitting on the runway, i look at the airport I get 15fps or so, look right and its 60fps… weird… Screenshots are at a freeware airport (C152) and payware Nelson NZ in the TBM.
nothing to do with pc spec…
My specs are R7 5800x. RTX3080Ti, 32gb, NVME hdd.




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I also noticed FPS drop 45 to 15 after 3 hrs flight Asobo A320 on route EGLL-LGAV.
At ramp after landing it was 15 FPS but when I reloaded the plane at the same location FPS jumped to 45 as usual.
GTX 980 4GB here, RAM 16 GB.

A short update.

So I picked up a new CPU+motherboard+RAM (still using the GTX 960 2 GB video card --prices are crazy).
CPU is now Ryzen 5 5600X
Motherboard ASUS ROG Strix B550F
Corsair 2x16GB at 3200 MHz

The behaviour is the same. I get a drop in framerate after the 5 minute mark. I thought it confirmed the video card hypothesis, but after doing more monitoring, I can correlate the framerate drop with the increase in temperature of my CPU (using stock heatsink+fan). At 80C the framerate drops to 10 FPS. When changing views from cockpit to external view, the CPU temperature decreases 10C and that is why the framerate increases back to ~50 - 70 fps.

So I plan on picking up a better cooling solution. Try to get the CPU below 80C in-flight. Hopefully that resolves this issue (for me).

I was able to find the culprit… It was the addons own AI… I disabled it to see if the problem went and yep it did…

addons own AI?

@WaysidePurse484 Which add-on?

I meant static aircraft… sorry… additional parked aircraft and stuff…

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NZA Nelson NZ but Im pretty sure Orbx YBBN has similar

So I am having the exact same issue, after a couple of minutes the fps drops to 10 fps. Reloading the aircraft works but after a couple of minutes the same issue raises.

In my case I have a i9 9900K, 64 gb ram and a 2080 Super so it has to be a application related bug.

the sim lost in performance today I went from 60 fps to 20 fps after 3 hours of flight on RTX 3080 Ryzen 3600x 32 Ram storage M.2