garageCube

Hi there.

I have a Madmapper 5.5.5 where FPS halves when the Madmapper-window isnt selected.

Engine is OpenGL
FPS is set manually to 50
Double buffer is on
Increase priority is on

There are plenty of headroom in both CPU and GPU power.

I am running windows 11

FPS is dropping when doing what ?
Dropping at which value ?
Do you play movies ? Shaders ?
What's your graphics card ? Drivers up to date ? On Windows if you have an integrated GPU (like an intel HD inside the CPU) and a discrete GPU (ie nVidia / AMD), you have to set the "Main Display" to a display connected to your discrete GPU.