Thought I'd try DirectX 12 on Windows 10 then upgrade to Windows 11 - gave me a c. 10% boost flying around Berlin (c. 30fps) and less tearing.  Still not as fast as DirectX11 but getting usable.

However, GPU usage is down below 10%, as low as 2% when at Tegel airfield ready for takeoff and only 5% over Berlin itself.

I'm using a 3090 with latest Nvidia drivers, AMD 3800X, 32 GB RAM and 80 Mbps Internet connection. Vsync and HAGS are off.

Any ideas welcome, and I'm happy to provide further information if required.

3 minutes ago, Malcolm Street said:

Thought I'd try DirectX 12 on Windows 10 then upgrade to Windows 11 - gave me a c. 10% boost flying around Berlin (c. 30fps) and less tearing.  Still not as fast as DirectX11 but getting usable.

However, GPU usage is down below 10%, as low as 2% when at Tegel airfield ready for takeoff and only 5% over Berlin itself.

I'm using a 3090 with latest Nvidia drivers, AMD 3800X, 32 GB RAM and 80 Mbps Internet connection. Vsync and HAGS are off.

Any ideas welcome, and I'm happy to provide further information if required.

Tearing depends only on the vsync setting. Also, you have no way to determine that you had a "10% boost" with Windows 11/DX12 unless you run a benchmark in controlled conditions (for example a landing challenge following exactly the same descent path, without changing views and with CapFrameX logging avg fps, 1% low, 0.1% low, etc.). Probably the "boost" was imaginary or due to different weather and AI traffic conditions.

Your Ryzen 3800X bottlenecks the 3090, that's for sure. However I suggest you to enable vsync, HAGS and avoid DX12 which is useless at the moment: lower performance and same graphics features.