Qlogic Corporation

Douglas A Prins

Gary S Dickinson

Gary E Schultz

A method and apparatus for determining the position of a head with respect to a rotating magnetic disk within a disk data storage device using standard signals output from a head/drive assembly (HDA). Servo zone detect pulses are used to determine the position of the read/write head with respect to the servo cells. An index pulse determines the angular position of the head. A servo zone counter is incremented by one in response to a servo zone detect pulse. Accordingly, the servo zone counter maintains a unique value which is corresponds to each data wedge on a surface of the disk. A servo clock has a constant number of cycles between sectors. The servo clock is coupled to the clock input of a sector counter. A sector pulse is generated and the sector counter is reset to zero when the number of cycles counted indicates that the beginning of a sector is under the read/write head. A sector ID counter counts the number of sector pulses. The output of the sector ID counter is equal to the sector ID of the sector which the read/write head is currently over. Thus, the data stored in the memory allows the present invention to determine the sector ID of the sector that the read/write head is over. Since the sector ID can be determined without being stored on the disk, at least some of the information which is normally recorded on the surface of the disk (i.e., the sector ID and associated fields) may be removed from the disk surface leaving additional room to store data.

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Huntington Beach, CA, United States of America

Douglas A Prins