Games - ROM image

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	Games - ROM image

A ROM image, or simply ROM, is a computer file which contains a copy of the data from a read-only memory chip, often from a video games cartridge or from an arcade machine's main board. The term is frequently used in the context of emulation, whereby older games are copied to ROM files on modern computers and can, using a piece of software known as an emulator, be played on the newer computer.

ROM images are also 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 system. At present, this article deals mainly with the use of ROM in relation to emulation.

Usage of ROMs

Changing Meaning

ROM chips, while still in use, have been replaced in many instances by optical media such as CD-ROMs and DVD-ROMs, magnetic media such as hard disks and magnetic tapes and, more recently, Flash Memory chips. However, the term ROM has grown to encompass many of these newer media so, for instance, a computer game copied from a magnetic tape may also be referred to as a ROM. Images copied from optical media are also called ISO images, after the standard file system for optical media, ISO 9660.

Dumping ROMs

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

Creating ROMs from other media is often considerably easier and can often be performed with off-the-shelf hardware. For example, the creation of ROMs from games stored on magnetic tapes (from, for example, the Sinclair ZX80 computer) generally involves simply playing the magnetic tape using a standard audio tape player connected to the line-in of a PC sound card. This is then recorded to an audio file and transformed into a ROM file using a simple program. Likewise, many CD and DVD games may be copied using a standard PC CD/DVD drive.

Copy prevention 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 unauthorised copying of modern games which are still commercially viable. Seeing this as potentially reducing sales of their products, many game distributors have incorporated 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 a non-standard 8 cm DVD-like optical media which for a long time prevented games from being copied to PCs. It was not until a hole was found in Phantasy Star Online Episode I & II that GameCube games could be successfully copied to a PC.

ROMs and Preservation

The lifespan of digital media is rarely great. While black-and-white photographs may survive for a century or more, many digital media can become unreadable after only a decade. This is beginning to become a problem as early computer systems may be, at the time of writing, fifty or sixty years old while early home video consoles may be nearing forty years old. Due to this aging, there is a significant threat that many early computer and video games may not survive without being transferred to new media. So, those with an interest in preservation are actively seeking older arcade and video games and attempting to dump them to ROMs. When stored on standardised media such as CD-ROMs and DVD-ROMs, they can be copied to future media with significantly reduced effort.

The trend towards mass digital distribution of ROMs, while potentially damaging to copyright holders, may also have a positive effect on preservation. While over time many original copies of older games may deteriorate, be broken or thrown away, a copy in ROM form may be distributed throughout the world, allowing games which would otherwise have been lost, a more robust survival.

Collecting ROMs

Like many other items such as Stamps and Coins, ROMs are also collected by many people. The motives for doing this vary from a desire to preserve the history of computer and video games to obsessive collectors. Those who desire to collect all ROMs have been derided by the team behind the MAME emulator as PokéROMs, in a reference to the Pokémon fad, Gotta Catch 'em All.

Given this desire by many people to collect ROMs, there are many projects on the internet which dump ROMs, catalogue them or provide tools to verify the correctness and completeness of ROM collections. For instance, the TOSEC and Good Tools projects produce regularly updated databases of games and other software for various old computers and video games consoles.

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