Proprietary optical disc format used in the Dreamcast video game console
The GD-ROM (gigabyte disc read-only memory) is a proprietary optical disc format developed as a collaboration between Sega and Yamaha for the Dreamcast.[1] A double-density format based on the CD-ROM[2] that could hold up to 1 GB, it consists of a single-density track near the disc's center surrounded by a double-density track comprising much of the disc's capacity.[1] The GD-ROM was created in response to developers exceeding the typical 650 MB storage capacity of the CD-ROM; while DVD-ROM would have addressed this limitation, implementing its then-new technology would have made console production cost prohibitive.[1] Along with the format's general novelty, the extra capacity also had the theoretical benefit of curbing video game piracy,[3][4] a major concern of CD-based consoles that was validated by its rampancy on the PlayStation.[5][6]
The Dreamcast was considered by the video game industry as one of the most secure consoles on the market with its use of the GD-ROM,[7] but this was nullified by a flaw in the Dreamcast's support for the MIL-CD format, a Mixed Mode CD first released on June 25, 1999, that incorporates interactive visual data similarly to CD+G.[8][9][a][b]Ahacker group self-named Utopia released their exploit in June 2000, having discovered that they could replace the visual data with Dreamcast code, enabling games burned onto CD-Rs to run on the console without any modding;[8][12] boot discs were initially used to facilitate this effort, but hackers subsequently discovered the ability to have burned games self-boot without the need for a boot disc.[12][13] While copying Dreamcast games onto a CD-ROM sometimes required the removal of certain game features, this did not affect their playability; such games were typically distributed on file sharing networks such as Internet Relay Chat.[12][14] Sega initially responded by aggressively pursuing cease and desist orders against online marketplaces selling pirated games, announcing the effort a month after the exploit's release;[7] the company eventually released a new revision of the Dreamcast hardware that removed MIL-CD support towards the end of 2000, closing the loophole.[15][16][17] Games released around that time also began to incorporate a more robust copy protection system to thwart illegitimate use.[18]
Before the Dreamcast was released, Sega "confirmed that Dreamcast owners will one day be able to upgrade the GD-ROM drive to DVD" as part of its general expansion system to keep it competitive against more powerful contemporaries.[19] In June 1999, The Nihon Keizai Shimbun reported on the development of a DVD distribution system by Sega alongside Hitachi, Nippon Columbia, and an additional partner; one known planned use for it involved encrypted multi-title releases that were to be accessed via downloadable product keys.[20] Despite displaying a Dreamcast DVD display unit at E3 2000,[21] the plans for a DVD add-on or fully separate unit never materialized during the short production run of the Dreamcast, rendering it the only sixth generation console to not adopt the format.
GD-ROM was also made available as an upgrade for the Dreamcast's arcade cousin, Sega NAOMI and the later Sega NAOMI 2, providing alternate media to its cartridge-based software.[22][23] It is also used as an option on both the Sega Chihiro and Triforce, respectively based on the Xbox and GameCube consoles.[24][25]
^The MIL-CD is only compatible with Japanese Dreamcast consoles due to regional lockout.[10]
^Unlike other mixed mode CDs, MIL-CD was capable of muting its data section from playback on typical CD players, preventing potential damage to connected speakers.[9][10] Some GD-ROM titles include such a warning as an audio track.[11]
