Editing ROM hacking (section)

===ROM expansion===

Generally speaking, a ROM hacker cannot normally '''add''' content to a game, but merely '''change''' existing content. This limit can be overcome through ''ROM expansion'', whereby the total size of the ROM image is increased, making room for more content and, in turn, a larger game. The difficulty in doing this varies depending on the system for which the game was made. For example, expanding an NES ROM may be difficult or even impossible due to the [[Multi-Memory Controller|mapper]] used by the game. For example, if a mapper allows 16 ROM banks and all of them are used, expanding the ROM further is impossible without somehow converting the game to another mapper, which could be easy or extremely difficult. On the other hand, expanding an SNES game (and even a Mega Drive (Genesis) game for that matter) is (relatively) straightforward. To utilize the added space, parts of the game code have to be modified or rewritten (see [[#Assembly hacking|Assembly hacking]] above) so the game knows where to look. Another type of ''ROM expansion'' that is fairly easy is [[Game Boy Advance]] ROMs. The ROMs themselves are generally small, but the memory space available sometimes exceeds it by multiples of up to 17.