There is a difference in Hyperthreading and Multithreading (multitasking).
Hyperthreading is an Intel name for taking each Core and providing
2 virtual Cores called Threads to process Instructions from the program.
AMD calls it SMT or something.
Multithreading is having a program (application) use all of the cores/threads
to run execution independently.
Non-linear processing. 4 cores or 8 threads can do simultaneous processing.
FS2020 (and other Games) cannot process as multithreading (Tile processing).
FS2020 is linear processing. The “Mainthread” processes instructions for itself
and the other threads ( gives them tasks to perform and waits for completion).
As such, it is a linear process. Accept an interrupt, do it or give it to a thread.
Wait for the completion before sending a display task to another thread to
display the results.
Thus, “mainthread” bottleneck.
Not much you can do about it and DX12 will not change it.
It is a linear process, not tile.
It is not a Windows issue, or processor issue or driver issue or anything.
It is a linear issue. One thing must happen before you can go on to the next thing.
For example, see an Alt Change interrupt from the pilot clicking the knob.
Give that instruction to a thread to get the Altitude.
Must wait for that thread to return the altitude and then display it and also do a task to perform the altitude change request from the pilot.
If you have a PC with 5 CPUs, the 5 still cannot run the program 5 times
as fast as 1 CPU.
Linear! With 5 CPU, 4 would be idle waiting on the 1 to complete.
We have to accept the concept of the “mainthread” bottleneck reality.