Can't do Multiple render window

As Soon as I add another Render Windows, My FPS goes to 20fps , my GPU goes to very lower usage but when I look at the dev mode display FPS, the gpu latency goes through the roof.

What am I doing wrong ?

Need details of your configuration

I’m running 3 monitors and find my FPS is 1/2 what I get with 1 monitor

5800X3D, 3080Ti, 32G RAM, 3x 1440p