If you found this file in a download or tutorial, please share more context so I can give a more precise answer about what it was intended to do.

It could be involved in the process of loading game data, providing a kind of key or patch for specific game titles to work properly with the emulator.

It is often reported to provide faster boot times, smoother gameplay, and reduced stuttering in demanding titles.

While specific details about the PSXONPSP660 BIN are scarce, it is believed to be related to the emulation or compatibility of PSX games on the PSP platform. The PSP was known for its ability to play a wide range of games, including those from the PSX era, through various emulation and porting efforts.