UPS, has also been developed by the ROM hacking community, designed to be the successor to IPS and PPF. A more recent patching format, the APS patching system, has also been developed by a devoted Game Boy Advance ROM hacker. The APS system is more space efficient, is reversible, and is faster than its predecessor. The purpose of distributing a hack in patch form is to avoid the legal aspects of distributing entire ROM images; the patch records only what has changed in the ROM, hence distributing it does not usually distribute parts of the original game. A patch is also normally drastically smaller than the full ROM image (an NES ROM can run anywhere from 8 KB to 2 MB; a Super NES ROM can run from 256 KB to 6 MB; and Mega Drive/Genesis ROMs can run from 512 KB to 4 MB). Also, since patches usually only contained user-made code changes and not copyrighted code, it was not illegal to distribute one. In a novel example of legal distribution, Sega released a Steam-based virtual hub for its previous collection of Mega Drive/Genesis games, entitled Sega Mega Drive Classics Hub. The Hub, besides allowing players to play emulated versions of these older games, takes advantage of Steam's support for user-created content through the Steam Workshop, officially allowing the distribution of ROM hacks of any of the offered games. Usage Patched ROMs are often played on emulators, however it is possible to play patched ROMs on the original hardware. The destination cartridge could be the original cartridge from which the initial unpatched ROM was pulled (which involves replacing the original ROM chip with a new one), or another compatible cartridge of the same type, such as flash cartridges. This is particularly popular for fan translations, homebrew games, prototypes, games for which ROM cartridges were never produced, or for games which require exact timing or other elements of the original hardware which are not available in emulators. Systems and games The majority of ROM hacking is done on NES and SNES games (including Sega Mega Drive/Genesis games to an extent), since such games are small and simple compared to games of more advanced consoles such as the Nintendo 64 or Nintendo DS. Games for the Game Boy, Game Boy Color and Game Boy Advance are also popular for hacking, as well as games for the PlayStation to a lesser extent.