System ROM



The system ROM (often called BIOS) is a ROM containing code for the 68k startup program, some lookup tables, and various generic functions which can or must be used by games. They are present in all NeoGeo hardware types in various versions. The NeoGeo CD system ROMs also contains graphics, sound, and code.

Original system ROMs have their nationality set by the byte at address $000401 (0=Japan, 1=US, 2=Euro), and their type set by the byte at $000400 (0=AES, $80=MVS).

Through-hole ROMs can be replaced by 27C1024 EPROMs.

=Hashes=

Copied from [MAME's source].

=Use=

The system ROM is always mapped at $C00000.

See:
 * System ROM calls
 * Hardware test
 * System ROM tables

=Home system=

Size: 128KiB. Named NEO-P0 (Japan) or NEO-EP0 (Export).

=MVS=

Size: 128KiB. Often named "SP" for System Program. Many different versions.

=CD/CDZ=





On CD systems, the system ROM contains and  programs, ADPCM sound, and graphics which are loaded to the corresponding DRAMs at startup. There are no SFIX or ROMs in CD systems (but still a  ROM).

Size: 512KiB.


 * FRONT-SP1 (Front loaders)
 * TOP-SP1 (Early top loaders using )
 * TOP-SP1-2 (Late top loaders using )
 * TOP-SPD (CDZ)

Hidden credits
The CD1 and CD2 system ROMs contain credits organized to be displayed on the fix layer (how can this be seen ?):




 * Noriyuki Higashi is the infamous "Mr.Noric".
 * Toshiya Yahara is cited as the inventor of the NeoGeo Pocket power supply in an SNK patent.
 * Jo(h)n Guso is credited as a programmer in several games.

Sound drivers
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.

=UniBIOS=

Hacked MVS system ROM with various added functionalities such as cheats, debug DIPs settings, region and system switch, CRC checking, a jukebox, error handling. See Universe BIOS.

=Neopen BIOS=

Opensource AES/MVS system ROM in development. See Neopen BIOS.