ZX Microdrive
Tape Data Recovery - ZX Microdrive
The ZX Microdrive is a magnetic tape storage system introduced by Sinclair Research. The first unit of ZX Microdrive was launched in July 1983 for Sinclair ZX Spectrum home computer. Later it was also used in Sinclair QL and ICL One Per Desk personal computers.
ZX Microdrives used tiny cartridges with dimensions 44 × 34 × 8 mm, carrying 5m endless loop of magnetic tape, 1.9 mm wide, driven at 30 in/second. A complete circuit is performed in approximately 8 seconds. Data was retrieved at the rate of 15kB/second.
The cartridges had a minimum capacity of 85kB when formatted. The real capacity depends on the number of bad sectors formed, and also the speed of the Microdrive motor when formatting. By multiple formatting, the capacity can be increased. This process causes the tape to stretch slightly, increasing the length of the tape loop and adding more sectors on it.
Microdrives, which were used in Sinclair QL, incorporated two internal drives. They were mechanically similar to the ZX Microdrive, but had different logical format, allowing each cartridge to hold at least 100 kB. They were slightly slower and had a take-up acceleration start instead of the instant start typical of the ZX Spectrum drives. Another feature of the QL Microdrives was that they used an expansion bus that allowed attachment of up to six external QL Microdrives. However, they were never commercially produced, may be because ZX Microdrives could be connected to a QL by putting a twist in the cable.
ZX Microdrives lost their reputation for unreliability. Also, the cartridges were relatively expensive, so they were replaced by similar technologies such as stringy floppy.
