International Business Machines Corporation

Dean C Palmer

Earl Albert Cunningham

Hal Hjalmar Ottesen

Jonathan Darrel Coker

Mark David Hagen

John Jeffrey Stephenson

Kevin Jack Erickson

Dana H Brown

Thomas C Christensen

Thomas W Glaser

Gregory J Kerwin

Richard H Estry

Richard C Jaworski

Jeffrey R Roepke

An apparatus and method for correcting for track misregistration when a slider or head assembly contains a separate read element and write element. The offset is determined at a first position and at a second position of the actuator arm assembly. From these offsets a constant and a multiplier are determined for determining an offset as a function of the cylinder location. Also disclosed is a method and apparatus for minimizing distance traveled to prevent misregistration when repositioning between the read element and a write element. The read element is intentionally offset from the write element at an angle so as to minimize the distance traveled across the disk.

Method and apparatus for positioning transducers to correct for read and

A magnetic disk drive channel circuitry is shown and described that generates eight incremental values of write current and eight incremental values of delta-V (the minimum voltage change per unit time which tests signals to discriminate between data and noise). Each of these variable parameter values may be program selected by a three bit bus signal. This variability testing of an adaptation to the optimum parameter value for each head media combination and by grouping tracks in contiguous data bands, the parameters may be optimized for tracks near the inner diameter, the outer diameter and in the middle band. The variable delta-V can also be used as an additional data recovery tool wherein re-reading with a lower value enhances recovery of missing bit errors and re-reading with an increased value can assist recovery from an extra bit error.

Compensation of write current adn delta-V for recording component and

The data recovery procedure for errors caused by track occlusion as a result of adjacent track misregistration or head sensitivity to the low frequency content of adjacent tracks is effected by reading and storing the information from the adjacent tracks and thereafter erasing the adjacent tracks either on centerline or with the transducer offset toward the intermediate track of interest. The track of interest can then be read with the transducer aligned with the track centerline and at varying positions of offset. If this sequence of rereads fails, the erase step can be repeated with greater amounts of offset toward the intermediate track to further reduce inband interference and the reread sequence also repeated.

Error recovery procedure using selective erasure

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Rochester, MN, United States of America

Dean C Palmer