An experimental eight-inch disc drive with one-hundred megabytes per surface

A net areal data density of 86 Kbits/mm2(56 Mbits/inch2) is achieved on an experimental disc system using ferrite heads and a longitudinal plated recording medium. Data is recorded at 20 Mbits/sec fully formatted in 2 Kbyte blocks. The ferrite Winchester head has a 0.46μm. (18 microinch) gap, a 16μm (625 microinch) trackwidth, and a flying height of 0.13 μm (5 microinches) at a head-medium speed (inside radius) of 9.7 m/s (382 inches/s. The track pitch is 20.8μm (819 microinches). The recording medium is a 72 KA/m (900 Oe) coercivity thin plated metal film. The data format and signal processing system permit random access to the data blocks during record and playback. Signal processing on playback includes Viterbi detection of class IV partial response, and double burst error correction. It was thus possible to record and recover over 100 Mbytes of data from one surface of a 200 mm (8 inch) diameter disc.