GD-ROM is the proprietary optical disc format used by the Sega Dreamcast. It is similar to the standard CD-ROM except that the pits on the disc are packed more closely together, resulting in a higher storage capacity: around 1.2 gigabytes. The format was developed for Sega by Yamaha. GD-ROM was also made available as an upgrade for the Dreamcast's arcade cousin, the Sega NAOMI, providing alternate media to its cartridge-based software. It is also used for the Sega Chihiro system board and can also be used by the Sega/Nintendo/Namco Triforce system board.