This might be fallout from the "wide" mode on non-2DS models. Can you see if it works in 0.8.4? It was added in 0.9.0.

You're right, it works perfectly fine in 0.8.4 though performance is quite a bit worse than 0.9.0, sometimes as much as 10 frames or so (btw is 0.9.0 supposed to perform better than 0.9.1? Because it does, not by much, but maybe 3 to 5 frames).

You're not the first person to report that it's slower, but I have no idea why it's slower. Nothing really should have changed that much.

Anyway, can you see if it works in this build? https://s3.amazonaws.com/mgba/build/mGBA-build-2021-05-10-3ds-6995-96988133b205cd127fe1e89812c94d1b9353f2d8.7z I had some code to detect if it was running on an o2DS but I think the code was broken.

Yes, the 800 pixel mode does not work on 2DS a̵n̵d̵ ̵p̵r̵o̵b̵a̵b̵l̵y̵ ̵a̵l̵s̵o̵ ̵n̵o̵t̵ ̵2̵D̵S̵ ̵X̵L̵. They only have 400 pixel screens (no 3D).

Yes, I know. I had code in there to detect and disable wide mode on 2DS. But it was likely broken.

Yes that build works, but just like normal 0.9.1 it seems to be a bit slower than 0.9.0, so I'm not sure whether I prefer a bit better performance or being able to use the top screen.

btw Pokemon Puzzle Challenge seems to be really demanding as even just sitting on the title or the menu the frame rate is in like the 30s.

I tested 0.8.4 and the performance in Pokemon Pinball is a vast difference between versions. 0.8.4 does display 90FPS or so when the game feels much slower. Not sure if 0.9.1 is again faster or slower than 0.9.0. I tested the build that was posted above and that seems to fix the issue.