The Triforce is an arcade system board developed jointly by Namco, Sega, and Nintendo, with the first games appearing in 2002. The name "Triforce" is a reference to Nintendo's The Legend of Zelda series of games, and symbolized the three companies' involvement in the project. The system hardware is based on the Nintendo GameCube with several differences, like provisions for add-ons such as Sega's GD-ROM system and upgradeable RAM modules. The Triforce was initially believed to have twice as much 1T-SRAM as the Nintendo GameCube (48MB instead of 24MB), but this was disproven by a teardown analysis of a Triforce board.
A few versions of the Triforce exist. The first two are the Type-1 and Type-3 units, the former using an external DIMM board (same as used on the Naomi and Naomi 2) while the latter integrates this component inside the metal casing. A custom Namco version exists which only accepts custom NAND Flash based cartridges, which has a different Media board and supposedly different baseboard. These boards use the same metal case design as the Type-3 Triforce.
Read more about this topic: List Of Sega Arcade System Boards