The original launch firmware; features a unique cursor and requires a CD to be present to open the player. Standard NTSC-U BIOS with the "Blue/Rainbow" UI design. v2.0
It tells the emulator how to behave like the original Sony hardware.
If you are setting up an emulator and find a file named ps1-rom.bin , it is likely a functional BIOS. To ensure it works:
Historically, “ROM” stands for Read-Only Memory. The PS1’s BIOS was stored on a chip on the console’s motherboard. Early emulation enthusiasts began calling the dumped file ps1-rom.bin because they were extracting the contents of that ROM chip.
Games did not contain drivers for the CD-ROM or memory cards; they relied on the BIOS to provide these services. Without the ps1-rom.bin file, an emulator is essentially an empty shell. The BIOS provides the API (Application Programming Interface) that game software expects to find in memory at addresses 0xbfc00000 (reset vector) and the syscall handlers.