Acknowledged wisdom from FSX days was that you had to have the fastest CPU you could get, and this was the case with xplane 11 too, and MSFS early days. But now I look at my performance stats while flying and my GPU is 100% and my CPU is doing almost sweet FA. This is probably good news for most since it’s easier to upgrade GPU than CPU.
4K?
I’m almost always CPU limited, especially in airliners. Ryzen 5800X, RTX 3080 at 1440p.
1440p, but same story on 4K monitor I’ve tried. 5700XT GPU, 3600xt CPU - often around 18% while GPU is at 100
I’m in that situation. RTX 2060super i7 10700k 1440p ultrawide which is harder to run the standard 1440p. CPU on average runs mostly below 20% or below GPU 100% with fps making out @50.
18% is the whole CPU average though, and MSFS is limited especially by one thread.
GPU at 100% shows you’re indeed not CPU limited, but you could still be right on the edge of being so.
Edit: Though with a 5700XT at 1440p I’d say you’re likely to be mostly GPU limited. At 1080p you might be more CPU limited.
So would an upgrade from a 5700XT to a 6700XT improve FPS significantly?
CPU matters most for people who are not GPU limited. If you are GPU limited now, and upgrade your GPU such that you become CPU limited, you will then want a faster CPU. 
I have a hunch that main thread limitation is the source of all evil plaguing us 
The CPU usage is low due to thread restrictions. So all the burdens are placed on the GPU. At present, we can only wait for DX12 to be officially launched to support multi-threading. At this time, it is not too late to study which is more important.
IMHO limited threads is the big problem. With my setup basically only the first two cores get used fully, while 3 and 4 are showing medium usage - no matter the settings in MSFS.
So it’s possible a superfast 16-core processor running at 5000 MHZ won’t give you significantly more performance than an 8-core running at the same clock speed.
Still there are several settings in MSFS specifically designed for CPU usage like LOD and glass cockpit. So I too hope for some improvement with DX12
I only see max FPS when my GPU is cranking at 95-100%… CPU% is of no concern. Although occasionally Windows puts all the non-MSFS processes on Core 0 and has MSFS running on the other cores… which is very strange… This may have happened when I was testing DX12….
It’s no hunch, the base of the sim does not lend itself to multithreading, main task limitation will always be unless it’s completely re-written from the ground up. This is why I disable virtual cores and run with the 8 true cores my CPU has (9900k) so I have the most available computing power in that one core working the main thread.
This is interesting, I got the 5700XT because I saw reviews describing it as a good match for the 3600X CPU, and I didn’t want to waste money on a better GPU only to find myself CPU limited. Wondering if it would be worth upgrading my GPU now and/or getting faster RAM (which I’ve read my AMD setup appreciates).
GPU at 100% shows you’re indeed not CPU limited
So by that logic, if my GPU is at 85%, you’re saying I AM CPU limited?
I often have 80-90% GPU, but dev mode is telling me I’m GPU limited.
So how does that fit together, any idea?
You’re probably about equally limited by both. You can test it pretty easily: turn down something that almost only affects the GPU. For example, set resolution scaling to 50% and see if your framerate increases. If it stays almost the same, you’re CPU limited; if it increases (especially by a lot), you’re GPU limited.
But as mentioned my guess is you’ll only gain a small amount of performance as they’re likely about evenly matched, with neither of them being a big bottleneck for the other.
Yeah i mean im definitely GPU limited in VR, but its close.
Which is why i will upgrade everything when the time comes!
You’ll always be limited by something. My experience is that in pancake mode it’s mostly CPU, where in VR it’s GPU. Also depends on the airplane, settings, screen resolution etc. There is no definitive answer. best too keep stuff balanced.
That kind of depends on the budget right? 3080Ti? Although … you will still be limited by GPU in scenario you depicted above, considering how low the CPU usage is. But you’ll maybe gain some frames.
If you flew the FBW A320 instead of a simple model like the one above I’m sure the numbers would look completely different.
The easiest way to tell if you are truly GPU limited is lowering the render resolution and noting the change in FPS. but it’s important to note your change in best case FPS and also your worst case.
For example with my machine I find that I am GPU limited 90% of the time, lowering my rendering resolution sees those high frame rates go even higher. However the other 10% of the time, I am being limited by my CPU Main thread, and lowering render resolution doesn’t help these moments. Although it happens rarely that I am CPU limited, it causes me the most problems with low frame rates and sometimes even stutter.
So if I were to upgrade my GPU I would get higher frame rates 90% of the time, and a faster CPU would help only 10% of the time, but where it truly matters for smooth performance, that 10% is the most important.
So for me, a faster CPU would benefit me the most. In particular a CPU with better single thread performance. Of course it would be more preferable for Asobo to better optimize the main thread, since replacing my whole cpu/mobo platform for a small increase single thread performance would probably not be enough to overcome all of the main thread issues.