Limited by main thread


I just bought a new PC and thought that I would be fine with it for Flight Simulator, but when I turn on the dev mode and display FPS, I get around 20 in the Airbus A320 in Heathrow.

The Tool says that it is “Limited by Main Thread”. Now I have a AMD Ryzen 5 3600 @3.6 Ghz, 16 GB Ram and an RTX 2060. I thought I would see better performance.

The game recommended High-End.

Any thoughts?


Have you checked this guide?
[HOW-TO] Graphics Settings and Performance Guide (SU12 Update) (7/26/2023)

Might help you tweak a little.


The thing is, even at Low settings the FPS stay the same.

The CPU should be capable to handle the sim. Usage is at about 50% in task manager.

Was considering to upgrade to the RTX 3080, but I‘m wondering if it would improve performance at all.


How are fps like with a GA in the open countryside? Here you should have 40 to 60.

I have the exact same issue, slightly different system but same low performance.
Ryzen 2600, RTX 2070, 16Gb RAM, game installed on Nvme ssd. Playing at 2560×1080
With the a320 at Charles de Gaulle, I get 15-20fps on any graphics settings, and same when I lower the resolution to 1920x1080.
Countryside in a dr400 or during the Balkans bush trip, I get between 30 to 40 fps in ultra, which is enough to play but I don’t think that’s the max my system can do.
There are loads of forum messages and reddit threads saying the same. It really looks like a bug, but whether it is Windows related, or game related, no one knows. There are even players with a 9900k and 2080Ti experiencing the same.

CPU usage is at around 60% on all threads, and 40% for the GPU

1 Like

Your hardware approximates the recommended spec.
Many people are having similar performance issues.
The next patch due end of September suggests significant improvements for CPUs with low core counts.

Use the Windows task manager, “Performance” tab, to watch the amount of %CPU and %GPU used

This way you know immediately who is the bottleneck

1 Like

Low core counts? I have 6 cores…

I know of windows task manager…the cpu is at 50% and graphics card is also around that percentage.

I have a newly built i7-10700k / RTX2070 / 32GB Ram. The game also recommends “high end” and I’m getting around 45-50 FPS. This is in a smaller aircraft (SR22) in Long Island NY (KISP) and Wichita, KS (KICT). (Note - running at 1080p although the RTX is up rendering then dropping to native resolution.)

I have read others see an impact based on the amount of buildings, density, etc.

My recommendation is try the same aircraft in a more mid-size city area. LOD (number of objects and detail) seem to hit the CPU more than other items. (Trees, bushes, etc.) That simple same setup different location may help narrow down to city / density versus specs.

Here you go…

1 Like

That’s the point, we see people with 4, 4/8, 8, 6/12 cores getting unexpectedly low performance. It’s some issue with their resource management and should be fixed next patch.

1 Like

Follow up… Sadly the latest patch did not improve performance for me in this area as I expected. Reading around, some people reported improvements others not. Perhaps the intermittent stutter was improved but not the general main thread slowness with high terrain detail.

I have an RTX 3080, 32GB RAM R9 3900xx cpu and in 1440p on default ultra setting I struggle to get above 30fps. I turned settings to low and still the same fps. CPU usage is at 20% and GPU usage at 40% and it still says " limited by main thread" in the developer overlay.

Absolutely shocking performance on such a high end PC. People with half my specs are getting the same or even better FPS than me.


I have almost the exact same system as you.

Ryzen 5 2600S, RTX 2060 Super, 32GB, SSD.

I’m only getting 20s in airliners at KJFK.

High-End presets.

I think to get decent rates in airliners near complex airports and big cities you will need a 7/9 series processor and at a minimum a 2080 Ti.

I fly GA and the occasional turboprop out of mostly smaller airports anyway so my FPS are usually around 45+.

I hope by the time the Aerosoft CRJ comes out the game engine is improved enough I can fly it at 24 FPS+ out of smaller regional airports.

My current upgrade plan is to a Ryzen 9 5900X and the rumored RTX 3080 Ti. Unless AMD pulls of something big with “Big Navi”.

if it’s just for MSFS, please don’t go for the 5900X, it has just too many cores, that flight sim won’t be able to take advantage of. It will also have 2 CCD’s.

Go with the 5600X or 5800X, 6 or 8 cores on a single CCD, a 19% IPC increase over the 3000 series, and the full 32MB of L3 cache available to all cores. The 5900X will simply be overkill. It will only be useful for heavily threaded (professional) workloads (editing, rendering, CFD analysis etc).

you would just be frustrated and asking 'why is MSFS only using 20% of my CPU if you went with the 5900X

I think is just a problem with the sim.
i am running a 3900XT, 2080TI, 32GB; MSFS2020 pretty much the only thing installed into a SSD disk, and cannot get above 20FPS in EGLL with the A320.
I am running everything on High except Clouds with AI off.
Resolotuion set to 1080.

1 Like

first thing; set the glass cockpit update rates to medium in the settings, that will most likely fix your issues in the glass cockpit planes, especially in the tubeliners.

Hi. Yes i am running medium update rates.

ah, though you said you were running all on ‘high’.

That’s rather odd then, your system should be running well above 20FPS with your hardware, especially on 1080p.
Something else must be going on, and since you’re saying you only have MSFS and windows installed, it can’t really be software (unless you’ve been messing with mods or editing files).

Take a look at your system temperatures. If stuff is overheating, it will clock itself down to protect itself. are CPU and GPU running hot? what frequencies are they running at, does the case have enough airflow. Stuff like that. Is everything configured correctly in your BIOS settings? (memory running at correct clockspeeds etc).

It’s extremely unlikely it’s a problem with MSFS, since people with lesser specs get better framerates than that, and people with the same specs as you are getting better framerates as well.

if you’re running mods, back up and remove the entire contents of the ‘community’ folder. See if that helps. After that, make sure the mods are up to date, and re-add them one by one, see which is causing the issue.

You can also check if the windows ‘System File Checker’ (SFC) to see if that pops up anything.

also check for windows updates, and make sure your chipset and graphics card drivers are up to date.

Hi I really appreciate your suggestions and feedback.
I’ve checked the BIOS and DOCP was set to off and RAM was running on 2133 instead of 3200.
I dont know if by itself that can cause a big impact on FPS. didnt check temps while using MSFS. On Idle the CPU is running around 45 degrees.
Reagrding mods i am only using Liveries and the A320 mod.

1 Like