The Quick Disk (QD) was a 3-inch floppy disk design launched by Mitsumi around 1985 (a prototype was shown in 1984). It was a much simpler design than other floppy disks of the time as it had no shutter mechanism to protect the disk surface from dust and used break-off tabs (rather than a sliding tab) for write-protection. In addition, rather than offer random access, data was recorded in a continuous spiral on the disk which took 8 seconds to read (in the 100 KB Triton QD drive) making them slow in use. Drives were single-sided and Quick Disks needed to be turned over to use the other side of the disk.
The design was used by Nintendo in its Famicom Disk System, with a modified casing that was longer. They were also used in some Smith Corona word processors where they were branded as DataDisk (and also sometimes labelled as 2.8-inch disks, referring to the size of the disk inside the casing).
The Quick Disk was used in some MIDI keyboards, samplers, sequencers and drum machines from manufacturers such as Roland, Korg, Akai and Yamaha. Quick Disk drives were also available for some mid-1980s home computers such as the Sinclair ZX Spectrum, the Dragon 32/64, and the Sharp MZ-700 and MZ-800.
Capacities varied from 100 KB to 256 KB.
The Quick Disk doesn’t appear to been around for long, though it lasted into the early 1990s in the form of the Smith Corona DataDisk and Nintedo Famicom Disk System. A 1991 review refers to the process of using the drive in a Smith Corona word processor as ‘slow (and strangely noisy) and expensive’.
Finding a working Quick Disk drive is difficult, and even if you can get one working (you’ll almost certainly need to replace the drive belt), reading data from the disks is likely to be very difficult due to bit rot.
Dimension (outer casing): 78.1 mm × 75.9 mm × 3 mm
Capacity: 100 KB to 256 KB