Before dissecting psxonpsp660.bin , we must understand what a BIOS (Basic Input/Output System) file is.

: Unlike original hardware BIOS files which are locked to Japan (scph5500), USA (scph5501), or Europe (scph5502), this file works with games from any region. Optimized Performance

It sits in a folder, unassuming. A few hundred kilobytes. No icon, no fanfare. Just a name: psxonpsp660.bin .