FPS drops and no change of fps with different quality (576 oder 1440)


My setup is:
AMD FX 6300 (six core)
Radeon R9 270x (2 GB)
8GB Ram
Zwift takes the high profile for my setup.
First problem is, that the fps rate is 60% of time around 60fps but it drops around every 30 sec. to around 17 fps for a period of about 10s. (Watopia)
For New york it is the same but with lower fps.
In this cases the gpu usage drops from 80 to 40%.
Anotzher thing is, that if I change the resolution in the game, the grafics quality changes according the resolution, but it has absolute no effect on the fps. Restarting the game has also no effect.
Thos means 20-60 fps in 1440p and 20-40 fps in 576p.

It is a freshly installed Win10 pro, With up to date drivers for the graphics adapter.

Does anybody have an idea?

regards Holger

That has been my experience as well since a few updates ago - big drops in FPS in group rides while solo rides are perfectly fine. My GPU is only 50% utilized which would indicate it isn’t getting instructions fast enough. Changing the resolution doesn’t improve things because the GPU isn’t the weakness. Dropping the foliage percent and turning off some of the graphics features makes no difference either. The strange part is that the CPU isn’t particularly taxed wither. I have no idea what’s up with that. Feels like some kind of deliberate timing thing, like waiting on network input before next render, or something in a spin hogging CPU. You’ll notice it more on that older AMD CPU. Win 7 SP1, latest Nvidia drivers, Core i5 4690K 3.5 Ghz, Nvidia GTX 970 4GB at 1080p Ultra profile.

I have run a now some rides with a core I5 9th gen 16gb RAM and gtx 2060 8Gb. There are of course no Problems. Fps rockstable AT 60fps.

I think IT is maybe the CPU the bottleneck.