3½ Inch Format


Sony introduced their own small-format 90.0 mm × 94.0 mm disk, similar to the others but somewhat simpler in construction than the AmDisk 3-inch floppy. The first computer to use this format was Sony's SMC 70 of 1982. Other than Hewlett-Packard's HP-150 of 1983 and Sony's MSX computers that year, this format suffered from a similar fate as the other new formats; the 5¼-inch format simply had too much market share.

Things changed dramatically when in 1982 the Microfloppy Industry Committee, a consortium ultimately of 23 media companies, agreed upon a 3½-inch media specification based upon but differing from the original Sony design. The first drives compatible with this new media specification were shipped in early 1983. In 1984 Apple Computer selected the format for their new Macintosh computers.Then, in 1985 Atari adopted it for their new ST line, and Commodore for their new Amiga. By 1988 the 3½-inch was outselling the 5¼-inch.

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Mitsumi's "Quick Disk" 3-inch floppies

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Another 3-inch format was Mitsumi's Quick Disk format. The Quick Disk format is referred to in various size references: 2.8-inch, 3-inch×3-inch and 3-inch×4-inch. Mitsumi offered this as OEM equipment, expecting their VAR customers to customize the packaging for their own particular use; disks thus vary in storage capacity and casing size. The Quick Disk uses a 2.8-inch magnetic media, break-off write-protection tabs (one for each side), and contains a see-through hole near center spindle (used to ensure spindle clamping). Nintendo packaged the 2.8-inch magnetic media in a 3-inch×4-inch housing, while others packaged the same media in a 3 inch×3 inch sq housing.

The Quick Disk's most successful use was in Nintendo's Famicom Disk System. The FDS package of Mitsumi's Quick Disk used a 3-inch×4-inch plastic housing called the "Disk System Card". Most FDS disks did not have cover protection to prevent media contamination, but a later special series of five games did include a protective shutter.


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