3.5 Inches FLOPPY

Amdek released the AmDisk-3 Micro-Floppy-disk cartridge system in December 1982.[8] Originally designed for use with the Apple II Disk II interface card, it has also been connected to other computers successfully.[9]

The drive itself was originally designed by Hitachi, Matsushita and Maxell. Only Teac outside this "network" is known to have produced drives. Similarly, only three manufacturers of media (Maxell, Matsushita and Tatung) are known (sometimes also branded Yamaha, Amsoft, Panasonic, Tandy, Godexco and Dixons), but "no-name" disks with questionable quality have been seen in the wild.

Amstrad incorporated a 3-inch single-sided drive into their CPC and PCW lines, and this format and the drive mechanism was later "inherited" by the ZX Spectrum +3 computer after Amstrad bought Sinclair. Later models of the PCW featured double-sided, double density drives.

While all 3-inch media were double-sided in nature, single-sided drive owners were able to flip the disk over to use the other side. The sides were termed "A" and "B" and were completely independent, but single-sided drive units could only access the upper side at one time.

The disk format itself had no more capacity than the more popular (and cheap) 5¼-inch floppies. Each side held 180 kiB for a total of 360 kiB per disk, and later 720 kiB for the PCW range.[10] Unlike 5¼-inch or 3½-inch disks, the 3-inch disks were designed to be reversible and sported two independent write-protect switches. It was also more reliable thanks to its hard casing (some reviews at the time reported driving over them with no problems).

3-inch drives were also used on a number of exotic and obscure CP/M systems such as the Tatung Einstein and occasionally on MSX systems in some regions. Other computers to have used this format are the more unknown Gavilan Mobile Computer and Matsushita's National Mybrain 3000. The Yamaha MDR-1 also used 3-inch drives.

Not a bad format in its own right, but the main problems were the high prices, due to the quite elaborate and complex case mechanisms. However, the tip on the weight was when Sony in 1984 convinced Apple Computer to use the 3½-inch drives in the Macintosh 128K model, effectively making it a de-facto standard.