c53ca59089360c4135f741ad47489512 (Use this to verify your file is authentic and not corrupted). Why Use This Specific BIOS?
It is part of the emulator engine that Sony developed to allow the PSP to play PSX games officially. psxonpsp660.bin bios file
Commonly used on low-powered devices like the RetroPie, PlayStation Classic modifications, and budget handhelds, PCSX ReARMed benefits immensely from the performance optimizations of the PSP BIOS. PlayStation Classic modifications
Open your emulator's BIOS configuration menu. Refresh the list or manually select psxonpsp660.bin as your primary system software. Legal Status and Safe Sourcing and budget handhelds
BIOS files are copyrighted material belonging to Sony. Distributing them is illegal. You are expected to dump this file from your own PSP (using 6.60 firmware) to be legally compliant. Conclusion