Why? PCSX-ReARMed is a dynarec (dynamic recompiler) core specifically designed for ARM architecture. The POPS BIOS was written for the PSP's MIPS + ARM hybrid. It's a perfect match.
: Some users report faster boot times and save/load speeds compared to standard retail hardware BIOS files. Fixes Black Screen Issues Psxonpsp660.bin Retroarch BETTER
Because Sony themselves created this file to run PS1 games on different hardware, it is essentially an optimized, all-in-one BIOS. It wasn't dumped from a clunky old console; it was built for software emulation. It's a perfect match
Disable "Enhanced Resolution (Slow)" in the core options. Set Internal Resolution back to 1x (Native). The POPS BIOS uses a different texture page alignment that hates upscaling in this specific game. It wasn't dumped from a clunky old console;
Unlike traditional BIOS files dumped from a physical PS1 (like scph1001.bin or scph5501.bin ), PSXONPSP660.bin comes from Sony’s (firmware 6.60).