Main thread bound? GPU bound? What does that REALLY mean?

User Support Hub Hardware & Peripherals
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Ref: The posting at Main Thread Limited - Raptor Lake:

This is another of my “manage my expectations” questions.

Recently I upgraded my graphics from AMD on-chip graphics to a Radeon RX 6800 card.

I ended up (essentially) reinstalling everything and my frame rates and performance have improved considerably. (No kidding Sherlock! :man_facepalming:)

I discovered the “frame rate” display in the developer options and enabled it. When I turned it on it gives me a lot of information that I am still trying to figure out, the most important seemed to be “main thread bound”.

I am guessing here, but I am assuming that what it’s telling me is that the CPU can’t keep up with the GPU, and/or the GPU is faster than the game needs.

Conclusion: If I am not having issues, don’t worry.

Corollary conclusion:
However, if I am having issues the solution is to take some of the load off the CPU somehow. (i.e. lower the CPU intensive graphic options, look at the task manager for cruft in the background, overclock or upgrade the CPU, etc.)

Conversely, if I am GPU bound I need to ease the load on the GPU, (or get a better one), if it’s causing problems.

I am also assuming that it is virtually impossible to get the CPU and GPU in exact lock-step so that neither is waiting for the other, so one of them will always be waiting for something.

Am I understanding this correctly?

Correlary question:
I am assuming that a comprehensive document on “Performance Tweaking MSFS” would be a book of non-trivial size, (by O’Reilly? :wink:), and is not something that is realistically within the scope of a forum posting.

However, are there guides that hit the “low hanging fruit” and are the simple fixes for the most common problems?

For example, I discovered that if I have too many scenery add-ons loaded in X-Plane 11, the frame rate tanks - the obvious solution being to “choose wisely” the scenery you are loading. I am assuming that this is true for MSFS as well.

Does a fairly large number of aircraft loaded, (in your “hanger”), cause problems too. (i.e. I have four or five additional aircraft in addition to the aircraft that are “built-in”.)

Is it possible to “tune” the scenery actually being used based on where I am? (i.e. If I am flying over Paris, I don’t need scenery or airport add-ons loaded for the United States, Dubai, Moscow Russia, or Bangkok Thailand.)

What other simple things can I check?

Thanks again for all your help!

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I think that you could have stopped there.

I am sure that gurus will come along with myriad suggestions but this is about as deep as most of us need to go:
If you want to maximise the performance, using your existing hardware, tune the settings until you see the most green, the least yellow and ideally no red in that highly intrusive frame rate counter and then switch it off.
If you are happy with your picture quality, the job is done and it costs nothing but a bit of your time.

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And I did!

One guy mentioned that world updates are often a source of stuttering and he always avoids them.

In X-Plane, scenery is controlled by the contents of the “Custom Scenery” folder and it can be customized for the area that you’re flying. For example, if I’m flying in Russia, I don’t load the US, England, Australia, or other places I don’t need. I don’t even load all of Russia, just the area I’m flying over. (I usually do short sightseeing flights.)

Can this be done in MSFS? Can I exclude places like the Japan, US, Canada, Germany, or other scenery packages if I’m flying over Greece or the outback in Australia - even though they might exist in the install - can I restrict the amount of scenery loaded?

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You can indeed, all you need is the Addons Linker and it’s freeware.

In my experience, with FS95, FS98, FS 2000, FS2002, FS2004, FSX, FSX-SE, P3D v4, P3D v5, X Plane 11, X Plane 12 , Aerofly and MSFS, the amount of active scenery has no effect whatsoever on frame rates but it does substantially lengthen the initial loading time.

I avoid “one guy mentions” subjective posts like the plague.

The best solution is to try it out for yourself.

Every PC is different and every PC user has theirs set up in a different way, which is why you can see so many posts saying “it doesn’t work at all”, followed by posts saying that “it works perfectly”

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If you are getting acceptable performance, turn off that nasty dev mode thing and go flying. It seems to me that whatever system you have, the frame counter will indicate that you are limited by either Mainthread or GPU. If you are having performance issues, then maybe do some analysis to see if your system is truly out of balance and do some in-sim settings adjustments.

FYI, when you are in “dev mode” your flights are not logged in your log book.