System ROM

BIOSes (officially called "SYSTEM ROM") are ROMs containing various generic functions and the startup program for NeoGeo systems. They are present in all hardware types.

The official BIOSes have their nationality set by the byte at address $C00401 (0=Japan, 1=US, 2=Euro). The Type is set by the byte at $C00400 (0=AES, 1=MVS).

(Enlarge) Configuration and book keeping menus in the SP-2 MVS BIOS

AES BIOS

Toshiba EP0 BIOS ROM found on an AES board

Size: 128KiB. Called "NEO-EP0".

MVS BIOS

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

Size: 128KiB. Called "SP-S2". Different names according to nationality.

Holds functions for coins, calendar and player starts.

CD/CDZ BIOS

File:Cd2 bios.jpg

SP1 BIOS ROM on a CDM3-2 board.

File:Brd spj.jpg

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

Size: 512KiB.

Chip that contains Z80 and 68k programs, PCM sound, and graphics which are copied to the corresponding DRAMs at boot time. The BIOS on CD systems also contains graphics and sounds. There is no SFIX or SM1 ROMs on cart systems.

The CD1 and CD2 BIOSes (FRONT-SP1 and TOP-SP1) include the "Ver 3.0 by Mr.Noric.1993/11/10 14:00" Z80 sound driver.

The CDZ BIOS includes the "Ver 3.0 by MAKOTO.04/03/10 to SK" driver.

The NeoGeo CD (not CDZ) BIOS contains credits, organized to be displayed on the fix layer (how can this be seen on screen ?):

CREDITS
SOFTWARE NORIYUKI HIGASHI
HARDWARE MOTOO YOKOYAMA TOSHIYA YAHARA
GRAPHICS OTIAI
SPECIAL  JON   GUSO
THANKS   CURRY SHIMIZU
SNK ALL STAFF

Noriyuki Higashi = Mr.Noric

Graphic visualisation of a CDZ BIOS dump, with separated data blocks:
File:Cdzbiosgfx.png