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A ROM image, or ROM file, is a computer file which contains a copy of the data from a read-only memory chip, often from a video game cartridge, or used to contain a computer's firmware, or from an arcade game's main board. The term is frequently used in the context of emulation, whereby older games or firmware are copied to ROM files on modern computers and can, using a piece of software known as an emulator, be run on a different device than which they were designed for. ROM burners are used to copy ROM images to hardware, such as ROM cartridges, or ROM chips, for debugging and QA testing.

Once games have been made available in ROM format, it is possible for users to make modifications. This may take the form of altering graphics, changing game levels, tweaking difficulty factor, or even translation into a language for which a game was not originally made available. Hacks can often take humorous forms, as is the case with a hack of the NES version of Mario Bros., titled Afro Mario Brothers, which features the famous brothers wearing Afro haircuts. The Metroid Redesign mod is a hack of Super Metroid that revamps the game and adds new objectives.

A large scene has developed to translate games into other languages. Many games receive a release in one part of the world,

ROMs can be copied from the read-only memory chips found in cartridge-based games and many arcade machines using a dedicated device in a process known as dumping. For most common home video game systems, these devices are widely available, examples being the Doctor V64, or the Retrode.

Dumping ROMs from arcade machines, which are highly customized PCBs, often requires individual setups for each machine along with a large amount of expertise.

Copy protection mechanisms

While ROM images are often used as a means of preserving the history of computer games, they are also often used to facilitate the unauthorized copying and redistribution of modern games. Viewing this as potentially reducing sales of their products, many game companies have incorporated so-called features into newer games which are designed to prevent copying, while still allowing the original game to be played. For instance, the Nintendo GameCube used non-standard 8 cm DVD-like optical media, which for a long time prevented games stored on those discs from being copied. It was not until a security hole was found in Phantasy Star Online Episode I & II that GameCube games could be successfully copied, using the GameCube itself to read the discs.

SNK also employed a method of copy prevention on their Neo Geo games, starting with The King of Fighters in 1999, which used an encryption algorithm on the graphics ROMs to prevent them from being played in an emulator. Many thought that this would mark the end of Neo Geo emulation. However, as early as 2000, hackers found a way to decrypt and dump the ROMs successfully, making them playable once again in a Neo Geo emulator.

Another company which used to employ methods of copy prevention on their arcade games was Capcom, which is known for its CPS-2 arcade board. This contained a heavy copy protection algorithm which was not broken until 7 years after the system's release in 1993. The original crack by the CPS2Shock Team was not a true emulation of the protection because it used XOR tables to bypass the original encryption and allow the game to play in an emulator. Their stated intent was to wait until CPS-2 games were no longer profitable to release the decryption method (three years after the last game release).[1] The full decryption algorithm was cracked in 2007 b

Dumping ROMs from arcade machines, which are highly customized PCBs, often requires individual setups for each machine along with a large amount of expertise.

While ROM images are often used as a means of preserving the history of computer games, they are also often used to facilitate the unauthorized copying and redistribution of modern games. Viewing this as potentially reducing sales of their products, many game companies have incorporated so-called features into newer games which are designed to prevent copying, while still allowing the original game to be played. For instance, the Nintendo GameCube used non-standard 8 cm DVD-like optical media, which for a long time prevented games stored on those discs from being copied. It was not until a security hole was found in Phantasy Star Online Episode I & II that GameCube games could be successfully copied, using the GameCube itself to read the discs.

SNK also employed a method of copy prevention on their Neo Geo games, starting with The King of Fighters in 1999, wh

SNK also employed a method of copy prevention on their Neo Geo games, starting with The King of Fighters in 1999, which used an encryption algorithm on the graphics ROMs to prevent them from being played in an emulator. Many thought that this would mark the end of Neo Geo emulation. However, as early as 2000, hackers found a way to decrypt and dump the ROMs successfully, making them playable once again in a Neo Geo emulator.

Another company which used to employ methods of copy prevention on their arcade games was Capcom, which is known for its CPS-2 arcade board. This contained a heavy copy protection algorithm which was not broken until 7 years after the system's release in 1993. The original crack by the CPS2Shock Team was not a true emulation of the protection because it used XOR tables to bypass the original encryption and allow the game to play in an emulator. Their stated intent was to wait until CPS-2 games were no longer profitable to release the decryption method (three years after the last game release).[1] The full decryption algorithm was cracked in 2007 by Nicola Salmoria, Andreas Naive and Charles MacDonald of the MAME development team.

Another copy prevention technique used in cartridge-games was to have the game attempt to write to ROM. On an authentic cartridge this would do nothing; however, emulators would often allow the write to succeed. Pirate cartridges also often used writable chips instead of ROM. By reading the value back to see whether the write succeeded, the game could tell whether it was running from an authentic cartridge. Alternatively, the game may simply attempt to overwrite critical program instructions, which if successful renders it unplayable.

Some games, such as Game Boy games, also had other hardware such as memory bank controllers connected to the cartridge bus. The game would send data to this hardware by attempting to write it to specific areas of ROM; thus, if the ROM were writable, this process would corrupt data.

Capcom's latest arcade board is the CPS-3. This was resistant to emulation attempts until June 2007, when the encryption method was reverse-engineered by Andreas Naive. It is currently implemented by MAME and a variant of the CPS-2 emulator Nebula.

Video game console emulators typically take ROM images as input files.

Software ROM

ROM images are used when developing for embedded computers. Software which is being developed for embedded computers is often written to ROM files for testing on a standard computer before it is written to a ROM chi

ROM images are used when developing for embedded computers. Software which is being developed for embedded computers is often written to ROM files for testing on a standard computer before it is written to a ROM chip for use in the embedded systems.

Digital preservation

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