First, a quick primer. The PSP (and later the PlayStation Vita) can run official software emulation for original PlayStation (PS1) games. To do this legally and accurately, Sony’s firmware includes a package of internal PS1 BIOS files renamed and repackaged for the PSP.

Based on community feedback (Reddit r/Roms, Emulation Wiki), the best verified item is: : psp_bios_pack (or similar). Direct file inside: PSP 6.60 BIOS/psxonpsp660.bin

Which follow-up would you like?

The search for the perfect emulation experience often leads to a specific, legendary file: . Originally optimized by Sony for "PSone Classics" on the PSP, this BIOS is widely considered the gold standard for stability and compatibility in the world of PlayStation 1 emulation. The Legend of the 6.60 BIOS

The Ultimate Guide to PSXONPSP660.BIN: The "Best" PS1 BIOS for Modern Emulation

Go to Settings > BIOS , click "Import BIOS," and select your .bin file. You can also manually place it in the bios folder located in your DuckStation directory.