Fullscreen only fills a corner of the TV

I’m trying to get RetroArch to run at 1920x1080 - fullscreen on my 4K TV. But i’m getting this:

I don’t want to set RetroArch at 4K because most emulators get slow. Windowed fullscreen works but also sets RetroArch at 4K so it’s slow. I read that the only way to keep the resolution you set is to run it fullscreen (real) but that only gets me this corner.

that’s with windowed fullscreen OFF/false, and video_fullscreen_x/y set to 1920x1080?

Yes. “windowed fullscreen mode” is OFF, “Start in fullscreen” is ON and resolution is set to 1920x1080.

I have had this exact same thing happen to me at least a dozen times… but I’m banging my head against the desk in frustration 'cause I can’t remember what I do to fix it.

I wanna say either something with the desktop zoom setting in Windows, or maybe this is when I have to put in a 0 in retroarch.cfg for it’s resolution settings, so it resets, essentially.

I’m sorry if that doesn’t help, I know it’s something like this though. Gonna keep thinking about it…