Here is the standard procedure to set up your MAME NeoGeo BIOS correctly.
If you are using RetroArch or a specific frontend like OnionUI, it is often recommended to place a copy in both the /BIOS (or /system ) folder and the /Roms/NEOGEO folder to ensure it is detected. Key Technical Details Advice on neogeo games in Arcade folder - RetroPie Forum mame neogeo bios
The "MAME NeoGeo BIOS" is not just one file. It is a collection of ROM files that dump the original BIOS chips. The exact set depends on your MAME version, but for modern MAME (versions 0.200 and above), you typically need a zip file named neogeo.zip . Here is the standard procedure to set up
To use UniBIOS, add uni-bios_4_0.rom (or latest version) to neogeo.zip and select it in MAME's (press Tab → Machine Configuration → BIOS ). It is a collection of ROM files that
Search for the set that matches your MAME version. Do not use random "universal" BIOS packs from 2010.
: Place the neogeo.zip file directly into your MAME roms folder alongside your game ZIP files.