System ROM

BIOSes are ROMs containing the initial program executed by NeoGeo systems. They are present in all hardware types.

AES BIOS

Toshiba EP0 BIOS ROM found on an AES board

128kB. NEO-EP0.

MVS BIOS

Toshiba SP-S2 BIOS ROM on a 1FZS MVS slot.

128kB. SP-S2. Different names according to nationality.

CD/CDZ BIOS

File:Cd2 bios.jpg

SP1 BIOS ROM on a CDM3-2 board.

512kB (1MB ?). One chip that contains Z80 and 68k programs, PCM sound, and graphics data which are copied to the corresponding DRAMs at boot time.

Graphic visualisation of a CDZ BIOS dump, with separated data blocks (larger size available):
File:Cdzbiosgfx.png

File:Brd spj.jpg

SPJ Japanese BIOS on a ROM-only arcade board. Picture courtesy of [MVS-Scans].