BIOSes (officially called "SYSTEM ROM") are ROMs containing the 68k startup program and various generic functions for NeoGeo systems. They are present in all hardware types in various versions. The NeoGeo CD BIOSes also contain graphics, sound, and Z80 code.
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, $80=MVS).
Size: 128KiB. Called "NEO-EP0".
Size: 128KiB. Called "SP-S2", "SP-E"... Different names according to nationality.
Graphic visualisation of sp-s2.bin:
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
Opensource AES/MVS BIOS in development. See Neopen BIOS.