The MiSTer Atari 2600 core was derived from the works of Retromaster.
The Atari 2600, originally sold as the Atari Video Computer System or Atari VCS until November 1982, is a home video game console from Atari, Inc. Released on September 11, 1977, it is credited with popularizing the use of microprocessor-based hardware and games contained on ROM cartridges, a format first used with the Fairchild Channel F in 1976. This contrasts with the older model of having dedicated hardware that could play only those games that were physically built into the unit. The 2600 was bundled with two joystick controllers, a conjoined pair of paddle controllers, and a game cartridge: initially Combat, and later Pac-Man.