The disk media that the Nintendo Famicom Disk System utilizes is a slight modification of Mitsumi’s “QuickDisk” 2.8″ square disk format. The double-sided FDS “Disk System Cards” hold 64KB (1KB = 1024 bytes) per side and are contained within a 3″ x 4″ housing. The majority of FDS disks were manufactured without a sliding cover to prevent media contamination in an effort to save money on production, but this was later included in a series of five blue disks games. Unlike most drives which store data in sectors, the FDS disks store data in continuous files in a long spiral, which has led some to compare it more to a tape-stream unit than a traditional random access disk drive.
Companies like Hacker International Co., Ltd. adopted a physical modification to Mitsumi’s QuickDisks to allow them to be used on a FDS. The small, detachable part attaches to the back of the disk and, along with a removal of the small tabs on the side of the disk, allows the disk to be inserted into the FDS and for the system to recognize it as a valid disk.
Piracy of Disk Cards became rampant through the use of the modified QuickDisks and the production of bootleg disks, as well as disk copying techniques. Hacker publications, such as Backup Technique and Famicom Kaizō Manual, showed the plans to make various devices to copy the disks along with very simple plans to convert QuickDisks to FDS disks. Thanks to Rob Budrick for the magazine advertisement.
Unofficial FDS Disks
Unofficial FDS disks are typically of lower quality than their official Nintendo counterparts and usually have absent or handwritten labels.
Official FDS disks were impressed with “Nintendo” at the bottom, which not only identified a disk as made for the FDS, but also permitted disks with the indentation to be correctly seated in the disk system due to matching raised “I” and “N” in the “NINTENDO” lettering inside the drive. To bypass this lockout feature without impressing “NINTENDO” into the disks, companies making unofficial disks either modified the spelling of “NINTENDO” to read “NINFENDO”, “NINIENDO”, or some other variant, or companies such as Mitsuya, Tiger, and Mag Disk simply used blank spaces where letters would normally be found on an official disk. This permitted the disks to seat without problems in an FDS drive.
Examples of Unofficial Disks
Game Doctor Disk Inserts
Disk inserts for Game Doctor format games (cart to FDS disk conversions) are typically made from heavyweight paper or color photos and are of very low quality. The disk cases are also typically of low quality and tend to break and crack easily.
Examples of Game Doctor Disk Inserts