Abstract: A method for writing servo patterns on at least one disc in a disc drive that has a first set of tracks and a second set of tracks on a major surface of the disc includes stepping between the tracks of the first set of tracks at a first constant angle, and stepping between the tracks of the second set of tracks at a second constant angle. Stepping between tracks in the first group or the second group includes selecting two adjacent tracks from either the first group of tracks or the second group of tracks, and determining the angle through which an actuator assembly must be rotated between the two adjacent tracks selected to produce a selected track pitch. The method produces a disc for a disc drive with a first set of tracks, and a second set of tracks in which the track pitch varies across the set of tracks.

Abstract: A method for writing servo information to a disc rotatably mounted to a spindle motor. A measured cage frequency is obtained from a written reference track, from which an actual cage frequency is predicted. The predicted cage frequency is then used to derive compensated position commands. During a servo write interval, the compensated position commands are used to control the head such that the head follows the disc movements caused by the cage frequency.

Abstract: A method for writing servo information to a disc rotatably mounted to a spindle motor. A measured cage frequency is obtained from a written reference track, from which an actual cage frequency is predicted. The predicted cage frequency is then used to derive compensatedposition commands. During a servo write interval, the compensated position commands are used to control the head such that the head follows the disc movements caused by the cage frequency.

Abstract: A servo writer writes servo information to at least one disc of a head disc assembly. The servo writer includes a clock head that writes a clock track to the at least one disc and generates a clock signal when the clock head reads the clock track on the at least one disc. A servo pattern generator writes servo patterns to the at least one disc in response to the clock signal generated by the clock head reading the clock track on the at least one disc. The servo track writer also includes a phase lock loop clock generator which synchronizes to the clock track and produces the clock signal for the servo pattern generator.

Abstract: A system, modules, means, and computer readable media for and a method of compensating disturbances that cause track shape irregularities on a disc in a disc drive during a disc servo-writing process performed by a servo-writer are disclosed. The disturbances substantially attributable to a nonrepeatable runout (NRRO) are present during the servo-writing process. A substantial component of the NRRO is a cage frequency generated by a spindle motor mechanism in the disc drive. A reference cage frequency is determined during a servo-writing process by using a position sensor. Then a feed-forward input signal is determined based at least on the reference cage frequency during the servo-writing process. In addition, the feed-forward input signal is feed-forwardly transmitted to the servo-writer.