You need a BIOS set that matches your MAME version.
For MAME to recognize the Neo Geo BIOS, follow these placement and configuration rules: mame neogeo bios
Many users prefer the Universe BIOS (UniBIOS) for its built-in cheat menus and region-switching capabilities. You need a BIOS set that matches your MAME version
Reconstructing the Neo Geo Boot Sequence and BIOS Operations Focus: Explains how the Neo Geo BIOS initializes hardware, checks cartridges, handles the “WARNING” screen, and manages the memory card system. Why it’s interesting: Directly maps to how MAME emulates the BIOS calls ( patch region, bank switching, interrupt handling). handles the “WARNING” screen
: These contain the 68k startup program and lookup tables used by games across all Neo Geo hardware.
: MAME is sensitive to versions. For the best compatibility, your neogeo.zip