ZX Microdrive
The ZX Microdrive is a magnetic-tape data storage system launched in July 1983 by Sinclair Research for its ZX Spectrum home computer. It was proposed as a faster-loading alternative to the cassette and cheaper than a floppy disk, but it suffered from poor reliability and lower speed.
Microdrives used tiny cartridges containing a 5-metre (200 in) endless loop of magnetic tape, which held a minimum of 85 KB and performed a complete circuit in approximately eight seconds.[1]
The Microdrive technology was later also used in the Sinclair QL and ICL One Per Desk personal computers.
Technology[edit]
Microdrives used tiny (44 mm × 34 mm × 8 mm (1.73 in × 1.34 in × 0.31 in) including protective cover) cartridges containing a 5-metre (200 in) endless loop of magnetic tape, 1.9 mm (0.075 in) wide, driven at 76 cm/s (30 in/s); thus performing a complete circuit in approximately 8 seconds. The cartridges held a minimum of 85 KB when formatted on a ZX Microdrive (exact capacity depended on the number of "bad" sectors found and the precise speed of the Microdrive motor when formatting). The data retrieval rate was 15 KB/s, i.e., 120 kbit/s. It was possible to "expand" the capacity of a fresh microdrive cartridge by formatting it several times. This caused the tape to stretch slightly, increasing the length of the tape loop, so that more sectors can be marked out on it. This procedure was widely documented in the Sinclair community magazines of the 1980s.
A total of eight ZX Microdrive units could be connected to the Interface 1 by daisy chaining one drive to the next via an electrical connector block.
The system acquired a reputation for unreliability.[2] The tapes stretched during use (giving them a short life span), eventually rendering the data stored unreadable. Also the "write protection" was software-based, thus a computer crash could erase the data on an entire tape in 8 seconds. The cartridges were relatively expensive (initially sold for £4.95 each, later reduced to £1.99).