Capstanless magnetic tape drive with electronic equivalent to length of tape

Claim 1

A magnetic tape drive operative with a host controller for reading and writing sequential data records comprising: transducer means for writing the data records on magnetic tape and for reading the data records therefrom; means for selectively moving the tape in forward and rearward directions past the transducer means; means for sensing a position of the transducer means on the tape; a cache memory for storing the data records to be written on, and the data records read from, the tape, a data storage capacity of the cache memory corresponding to a predetermined length of the tape and having forward and rearward boundaries; and circuitry means connected to the transducer means, tape moving means, transducer position sensing means and cache memory for generating a logical head that moves forwardly and rearwardly through the cache memory as the data records are written into and read therefrom, for controlling the tape moving means to cause a corresponding position of the transducer means to approach a position of the logical head during a write operation, and for causing the position of the logical head to approach the corresponding position of the transducer means during a read operation so that delays due to accelerations and decelerations of the tape moving means are masked and the host controller can instantaneously read data bi-directionally and instantaneously switch between read and write operations.