A double-density format based on theCD-ROM[2] that could hold up to1 GB, it consists of a single-densitytrack 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 typical650 MB storage capacity of the CD-ROM; whileDVD-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 curbingvideo game piracy,[3][4] a major concern ofCD-based consoles that was validated by its rampancy on thePlayStation.[5][6]
The Dreamcast was considered by thevideo 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, aMixed Mode CD first released on June 25, 1999, that incorporates interactive visual data similarly toCD+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 ontoCD-Rs to run on the console without anymodding;[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] The main protection was to scramble the EXE file on the disc. The Dreamcast console would unscramble it in memory if a GD-ROM was inserted; however when loading from an MIL-CD, the EXE file was loaded directly into memory, bypassing the copy protection[14]. 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 onfile sharing networks such asInternet Relay Chat.[12][15] Sega initially responded by aggressively pursuingcease 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.[16][17][18] Games released around that time also began to incorporate a more robust copy protection system to thwart illegitimate use.[19]
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.[20] In June 1999,The Nihon Keizai Shimbun reported on the development of a DVD distribution system by Sega alongsideHitachi,Nippon Columbia, and an additional partner; one known planned use for it involved encrypted multi-title releases that were to be accessed via downloadableproduct keys.[21] Despite displaying a Dreamcast DVD display unit at E3 2000,[22] the plans for a DVD add-on or fully separate unit never materialized during the short production run of the Dreamcast, rendering it the onlysixth 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 laterSega NAOMI 2, providing alternate media to its cartridge-based software.[23][24] It is also used as an option on both theSega Chihiro andTriforce, respectively based on theXbox andGameCube consoles.[25][26]
^The MIL-CD is only compatible with Japanese Dreamcast consoles due toregional lockout.[10]
^Unlike other mixed mode CDs, MIL-CD was capable of muting its data section from playback on typicalCD players, preventing potential damage to connected speakers.[9][10] Some GD-ROM titles include such a warning as an audio track.[11]
^abcdHagiwara, Shiro; Oliver, Ian (November–December 1999). "Sega Dreamcast: Creating a Unified Entertainment World".IEEE Micro.19 (6):29–35.doi:10.1109/40.809375.
^"Dreamcast Expandability"(PDF).Electronic Gaming Monthly. Vol. 122. Ziff Davis. September 1999. p. 204.Archived(PDF) from the original on 2023-04-04. Retrieved2020-06-18.
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