Mapper hack

A mapper hack is a game ported from one board which contains all the game's data and sometimes tiles to another, making it more simple and easier to reproduce. This feature is somewhat well-known among the romhacking community, although, in order to save spendings, pirates also exploit this feature. In certain cases, this results in the final result being drastically butchered compared to the original. Mapper hacks are also often made to work on new bootleg reproduction cartridges or multicarts. In the case of official games, these are usually converted from MMC1 to MMC3 because the former mapper doesn't work on most multicarts.

Sometimes, dumpers use this technique in order to make bootleg games with complicated mappers work on most emulators. The most well-known example of post-dumping hacking is Kart Fighter.

Examples

Hacks of bootleg games

• Super Lion King two versions are known to exist. The original one shows the Super Game logo for a longer period of time and has the Bug Toss minigame. The mapper hack, despite maintaining most of the game's data, removes this minigame, although leaving the bonus item available.
• Aladdin by Super Game has a mapper hack with only four levels available, as well as several graphical glitches. The full version has been discovered, with most of the levels from the original game available, as well as the actual intermission graphics from there, contrary to these ripped from the Sega Mega Drive version of Prince of Persia.
• Aladdin by Hummer Team is also known to have at least two MMC3 hacks. The more commonly distributed one lacks in-game music and background animations whereas the other one includes these.
• Ture MK3 has one known as Mortal Kombat 4. Contrary to the fact that mapper 4 boards can actually hold 256K CHR-ROMs, Mortal Kombat 4 automatically cuts half of the graphics present in the original version, which results in having a regular 128K CHR-ROM. (The original game was 384K, having an extra 128K of graphics) In the mapper hack, there are only four unique fighters and three stages, yet most of the music is buried inside the game's data. The removed characters are still present by name, but are essentially the same as the four characters retained in this version.
• Samurai Shodown by Rex Soft has one named Samurai Shodown III. In order to look more like its original version, it duplicates the roster not twice, like before, but thrice.
• Street Fighter Zero 2 '97 already had two sets of repeating fighters originally, but because MMC3 can't have a 512k CHR-ROM, the mapper hack leaves only four original fighters intact, plus no intro cutscene. Unlike this game, The King of Fighters '96 has already been ripped, mainly because Ka Sheng never produced cartridges with memory bigger than 512K.
• Street Fighter II Pro by Cony Soft has several mapper hacks available. One of them is Street Fighter V, which duplicates the cast, yet removes Sagat and M Bison/Vega from the roster, and replaces Ryu's icon with Goku's. Another one, included on multicarts quite frequently is Street Fighter VI which uses even more simplified graphics for the main menu and removes Dhalsim and Zangief. Both of them use only two unique stages, which use different palettes depending on whom the player is fighting.
• Mortal Kombat II has one, which duplicates all of the fighters in the roster, but keeps the content intact. Another one, included on 10000000-in-1 multicart, is possibly 256K big, compared to the original (which was 384K). Despite this hack having every fighter from the original, the stages were drastically simplified.
• Boogerman has no sound on Super 303 3-in-1 multicart, which may provoke a guess that this multicart have used the mapper hack of this game.

Hacks of licensed games

• On multicarts, Tengen Tetris, Arkanoid, TwinBee, and City Connection (normally based on mapper 3 for the former two and 87 for the latter two) are commonly included in NROM/mapper 0 format as opposed to the original mappers they used. This results in the games having fewer graphics than the original versions, causing graphical glitches in the latter three. Tetris has its title screen and high score screen removed to prevent this.
  • Several other NROM conversions exist in this style, for games such as BPS Tetris, Hokuto no Ken, and Dr. Mario, though these conversions are much less common to find.
• Several early Famicom titles run on "mapper 185" - effectively an NROM board with added copy protection. Multicarts featuring these games will remove the copyright protection and convert them to standard NROM; the most commonly converted games are Bird Week and Mighty Bomb Jack.
• Despite CNROM/mapper 3 games being common on multicarts, the majority of multicarts do not contain CNROM support. CNROM games are generally converted to the multicart's own proprietary mapper; in rare cases, they may be converted to MMC3.
• While most NES titles use CHR-ROM for graphics (i.e. a separate graphics chip on the circuit board), some games instead use CHR-RAM, combining the graphics data into the program data. Presumably for compatibility with a CHR-ROM chip, some multicarts convert CHR-RAM games to CHR-ROM format; the games are also converted to MMC3.
  • The most common game to be converted to CHR-ROM is Contra, based on the US version. At least three bootleg CHR-ROM conversions exist; one conversion (seen on some "KT Series" multicarts) removes levels 2, 4, and 5 from the game, while the other two retain all levels. CHR-ROM conversions were also produced for DuckTales and The Little Mermaid, though these are less common.
• Basic MMC1 to MMC3 conversions were created for numerous games; for these conversions, there are generally no aspects of the gameplay/graphics altered or missing. Some notable examples include Chip 'N Dale Rescue Rangers 1 and 2, Snow Bros., and Kero Kero Keroppi 2.
• Beginning in the 2010s, several types of "customizable" multicarts were produced - allowing the purchaser to choose the games featured on the cartridge. These multicarts are generally only produced in Eastern European countries, and feature a very large amount of (generally MMC3) mapper hacks.
  • The developer "Cluster" created a multicart builder program in 2015, based on the technology used in the CoolBoy multicarts. Many MMC3 conversions were created for this multicart builder - roughly 200 total - including otherwise-uncommon games such as Bubble Bobble, Snake Rattle 'n' Roll, and Nintendo's NES version of Tetris.
  • A similar customizable cartridge known as the "CoolX-Lite" was produced by several Ukrainian developers. Very extensive MMC3 conversions were developed for the CoolX; some notable titles include Mr. Gimmick and Punch-Out!!, as well as bootleg games such as Donkey Kong Country 4, Tiny Toon Adventures 6, and Toy Story.
  • While both the Cluster and CoolX multicarts are intended to be purchased on cartridge, the individual MMC3 hacks are publicly accessible online.
• Spider-Man: Return of the Sinister Six has a mapper hack, which reduces the size of the game from 384K to 256K, removing most of the cutscene graphics in the process. This version is sometimes included on multicarts. Oddly, some versions of this hack retain the copyright while others don't.