Abstract: A phase modulated servo method and apparatus are provided for use in a disk file. The disk file includes at least one disk mounted for rotation about an axis and the disk has at least one disk surface for storing data. At a predefined location of the disk surface a series of servo tracks of a predetermined high gain servo pattern are written. The predetermined high gain servo pattern includes 360° phase difference information within each data cylinder. The servo tracks are detected for identifying servo phase information.

Abstract: In a ultra high density, multiple-disk drive, track switches within a cylinder of tracks as well as track switches to tracks on other cylinders both require a movement of the head stack actuator. Track switching latency in such a disk drive is reduced by overlapping pre-movement portions of the track switching process with the data transfer operation of the currently active recording head. In addition, post-movement portions of the track switching process are overlapped with the movement of the heads so that the next selected read/write head may begin a data transfer operation immediately upon arrival at the next track. Further, the pre-movement and post-movement portions of the track-switch process may be overlapped with low displacement movement of the read/write heads relative to the currently active track or the next track.

Abstract: A method and an apparatus for optimizing movement of a disk drive's head actuator arm away from a magnetic latch that holds the arm in a parked position at the Inner Diameter (ID) of a disk. Current energizing of the arm's actuator motor moves the arm away from the magnetic latch and is controlled to compensate for any change in magnetic holding force. When the disk drive is powered up, a current pulse of one polarity is applied to the actuator motor. This initial current pulse normally moves the arm away from the magnetic latch and is followed by a current pulse of the opposite polarity to decelerate movement of the arm. If this initial sequence fails to move the arm away from the magnetic latch, the magnitude of the two current pulses is increased, and the opposite polarity pulse is followed by a small magnitude current of the one polarity. The read signal from the head is monitored to indicate that the arm has moved into the disk's central databand area, and then into the disk's Outer Diameter (OD) area.