System ROM
The system ROM (often called BIOS) is a ROM containing code for the 68k startup program, lookup tables, and various generic functions which can or must be used by games. They are present in all hardware types in various versions. The NeoGeo CD system ROM also contains graphics, sound, and Z80 code.
The official system ROMs have their nationality set by the byte at address $000401 (0=Japan, 1=US, 2=Euro).
The type is set by the byte at $000400 (0=AES, $80=MVS).
Included lookup tables
- $C02000: METRIC_DATA (?, $2000)
- $C04000: Sinus table (words, signed $200)
- $C04200: Random table ($100)
To do: Which games use them ?
AES
Size: 128KiB. Called NEO-EP0.
MVS
Size: 128KiB. Called SP-S2, "SP-E"... Different names according to nationality.
Graphic visualisation of sp-s2.bin:
CD/CDZ
Size: 512KiB.
- FRONT-SP1 (Front loader)
- TOP-SP1 (Top loader, LC8953)
- TOP-SP2 (Top loader, LC98000)
- TOP-SPD (CDZ)
Contains Z80 and 68k programs, PCM sound, and graphics which are copied to the corresponding DRAMs at boot time. There is no SFIX or SM1 ROMs in CD systems (but still a LO ROM).
The CD1 and CD2 system ROMs (FRONT-SP1 and TOP-SP1/SP2) include the "Ver 3.0 by Mr.Noric.1993/11/10 14:00" Z80 sound driver.
The CDZ version includes the "Ver 3.0 by MAKOTO.04/03/10 to SK" driver.
The CD1 and CD2 system ROMs contain 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 is the infamous "Mr.Noric".
Toshiya Yahara is cited as the inventor of the NeoGeo Pocket power supply in an SNK patent.
Graphic visualisation of a CDZ BIOS dump, with separated data blocks:
File:Cdzbiosgfx.png
UniBIOS
Hacked MVS system ROM with various added functionalities such as cheats, CRC calculation, jukebox, error handling. See Universe BIOS.
Neopen BIOS
Opensource AES/MVS system ROM in development. See Neopen BIOS.