NAME

rgbfix — Game Boy checksum fixer

SYNOPSIS

rgbfix

[-CcjsVv] [-f fix_spec] [-i game_id] [-k licensee_str] [-l licensee_id] [-m mbc_type] [-n rom_version] [-p pad_value] [-r ram_size] [-t title_str] file

DESCRIPTION

The rgbfix program changes headers of Game Boy ROM images. It also performs other filetype operations, such as truncation. The arguments are as follows:

 

 

-C

Set the Game Boy Color–only flag: 0x143 = 0xC0. If both this and the -c flag are set, this takes precedence.

 

 

-c

Set the Game Boy Color–compatible flag: 0x143 = 0x80. If both this and the -C flag are set, -C takes precedence.

 

 

-f fix_spec

Fix certain header values that the Game Boy checks for correctness. Alternatively, intentionally trash these values by writing their binary inverse instead. fix_spec is a string containing any combination of the following characters:

l

Fix the Nintendo logo (0x104–0x133).

L

Trash the Nintendo logo.

h

Fix the header checksum (0x14D).

H

Trash the header checksum.

g

Fix the global checksum (0x14E–0x14F).

G

Trash the global checksum.

 

 

-i game_id

Set the game ID string (0x13F–0x142) to a given string of exactly 4 characters. If both this and the title are set, the game ID will overwrite the overlapping portion of the title.

 

 

-j

Set the non-Japanese region flag: 0x14A = 1.

 

 

-k licensee_str

Set the new licensee string (0x144–0x145) to a given string, truncated to at most two characters.

 

 

-l licensee_id

Set the old licensee code, 0x14B, to a given value from 0 to 0xFF. This value is deprecated and should be set to 0x33 in all new software.

 

 

-m mbc_type

Set the MBC type, 0x147, to a given value from 0 to 0xFF.

 

 

-n rom_version

Set the ROM version, 0x14C, to a given value from 0 to 0xFF.

 

 

-p pad_value

Pad the image to a valid size with a given pad value from 0 to 0xFF. rgbfix will automatically pick a size from 32KiB, 64KiB, 128KiB, ..., 8192KiB and give a warning thereafter. The cartridge size byte (0x148) will be changed to reflect this new size.

 

 

-r ram_size

Set the RAM size, 0x149, to a given value from 0 to 0xFF.

 

 

-s

Set the SGB flag: 0x146 = 3.

 

 

-t title

Set the title string (0x134–0x143) to a given string, truncated to at most 16 characters. It is recommended to use 15 characters instead, to avoid clashing with the CGB flag (-c or -C). If both this and the game ID are set, the game ID will overwrite the overlapping portion of the title.

 

 

-V

Print the version of the program and exit.

 

 

-v

Equivalent to -f lhg.

EXAMPLES

Most values in the ROM header are only cosmetic. The bare minimum requirements for a workable image are checksums, the Nintendo logo, and (if needed) the CGB/SGB flags. It is a good idea to pad the image to a valid size as well (“valid” meaning a multiple of 32KiB). The following will make a plain, no-color Game Boy game without checking for a valid size: The following will make a SGB-enabled, color-enabled game with a title of “foobar”, and pad it to a multiple of 32KiB. (The Game Boy itself does not use the title, but some emulators or ROM managers might.) The following will duplicate the header (sans global checksum) of the game “Survival Kids”:

SEE ALSO

rgbasm(1), rgblink(1), rgbds(7)

HISTORY

rgbfix was originally released by Carsten Sørensen as a standalone program called gbfix, and was later packaged in RGBDS by Justin Lloyd. It is now maintained by a number of contributors at https://github.com/rednex/rgbds.