I found a post like this on reddit.com , does it work I don't know. I don't have an AMD card..
"Hey! Found a simple but strange workaround. Ive been having this problem trying to run the emulator in default settings. Turns out, at least in my case, setting the emulator to render to my native monitor resolution lets me run in fullscreen at full 60 fps, using about 49% of GPU according to task manager. Any other resolution I choose cuts the frame rate in half when going to full screen.
This made me think maybe it has something to do with the scaling settings in Adrenalin, so I disabled integer scaling- and what do you know? Every resolution I choose to render can now be rendered at full speed in full screen mode, but if I choose a 4:3 resolution instead of a 16:9 one,the image is stretched. 16x9 resolutions are not stretched, just have the necessary black bars on the sides.
In the end, now Im not even sure this is the same problem that Ian was speaking about when posting to AMD, but this workaround seems to work like a charm for the specific issue I was experiencing, so I hope it helps someone who is interested in using this emulator."