You want the fastest possible boot times without the Sony "Diamond" logo sequence. How to use it
Search for psxonpsp660.bin accompanied by the labels "updated," "modified," or Check SHA-1 hashes on trusted PSP communities:
However, for purists and those troubleshooting a specific game that refuses to boot, psxonpsp660.bin remains a crucial artifact. It represents the pinnacle of Sony's own emulation efforts on the PSP, liberated by the community to ensure that the "Better" experience was available to everyone, not just the digital storefront.
If you still take your PSP on commutes, or if you have a backlog of PS1 classics on your memory stick, using the standard bin is actively harming your experience.