GD-ROM
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 and other Sega systems. == Specification == A double-density format based on the CD-ROM 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.