PSOne MM3 mod chip install. There are many others like it, but this one is mine. : r/psx
PsNee on PU-23 board - Project Guidance - Arduino Forum
Darthsternie on Twitter: "Anybody who knows anything about PS1 Modchips able to help me tell what this modchip could be? I can't these solder points anywhere online. It's a PSOne with 12c508A