Many classic arcade boards (like Galaga or Donkey Kong ) had all necessary system code embedded directly into the game ROM set. These are "self-contained." However, modular arcade systems—like the Neo-Geo MVS, Capcom Play System (CPS-1/2), and Sega System 16—were designed with interchangeable game cartridges or daughterboards. For these, the BIOS lives on the motherboard, separate from the game.
BIOS files evolve. Ensure your BIOS pack matches your version of MAME to avoid "Checksum Error" messages. all mame bios