MAME is not the only emulator that needs a CPS2 BIOS. Other arcade emulators have their own requirements.
Crucially, Capcom implemented a heavy security system called the . This battery kept a small portion of the BIOS’s memory alive. If the battery died, the encryption keys vanished, and the board became a brick. This makes preserving BIOS dumps critical for history. mame cps2 bios
"Required ROM/BIOS images not found: cps2.rom (BAD CRC)" MAME is not the only emulator that needs a CPS2 BIOS
Launch MAME via command line: mame sfiii (for Street Fighter III: New Generation ) the encryption keys vanished
This is what most people use today. When you download a "MAME CPS2 BIOS" from a standard set, you are likely downloading: