Most PS1 BIOS files (like SCPH-5501) were dumped from original physical hardware consoles. However, psxonpsp660.bin was created by Sony specifically for the PlayStation Portable’s "PS1 Classics" emulator.
It runs almost every regional title (NTSC-U, PAL, and NTSC-J) without needing separate BIOS files for each. Psxonpsp660.bin Retroarch BETTER
Sony optimized the code to skip unnecessary hardware checks, getting you into your game faster. Most PS1 BIOS files (like SCPH-5501) were dumped
Obtain the psxonpsp660.bin file (it is usually 512KB). Psxonpsp660.bin Retroarch BETTER