The Amdek Amdisk-III

written by Matthew Reed

Amdek advertisment from 80 Micro

Amdek advertisement from the
July 1983 issue of 80 Micro

The Amdisk-III was an external dual-3″ (not 3½″) floppy disk system introduced by Amdek Corporation in 1982. The TRS‑80 Model III version was originally priced at $899, but that price was soon reduced to $599 and later $499. Versions were also available for the TRS‑80 Color Computer, the IBM PC, and the Atari 400/800. 80 Micro tested a prototype version for the Model I, but it is unclear if that Model I version was ever sold. Amdisk also sold a single-drive system, the Amdisk-I, that was only available for the Apple II.

In 1982 to 1983, there were four “microfloppy” formats competing to replace the 5¼″ floppy:

  • Sony hard-shelled 3½″
  • Hitachi hard-shelled 3″
  • Tabor soft-shelled 3.25″
  • IBM hard-shelled 3.9″ (announced but never actually produced)

The Amdisk-III followed the Hitachi 3″ microfloppy standard and its drives were capable of both double-density and double-sided operation. The drives themselves were plug-compatible with 5¼″ drives and the unit plugged directly into the external floppy drive connector on the Model III.

The Amdek advertisements promised a formatted capacity of 736K, or 368K per side. The Amdisk-III came with two 3″ disks. At the time, a box of ten 3″ disks cost around $55 on average.

Amdek continued advertising the Amdisk-III throughout 1983. However, in 1984 Apple chose the Sony 3½″ drives for their Macintosh computer. The Sony format became the de facto microfloppy standard and the other formats, including the Hitachi 3″, were soon forgotten. But the 5¼″ disk format still had plenty of life left in it; it wasn’t until 1988 that 3½″ drives finally outsold 5¼″ drives.

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