Abstract: An error logging method utilizes a temporary defect list to store errors produced at or above a predetermined occurrence frequency during a defect detecting test. The method includes the steps of: determining whether an error is recorded on a temporary defect list, determining whether the error is recorded on an error frequency list when the error is not recorded on the temporary defect list, adding the error to the error frequency list if the error is not recorded on the error frequency list, increasing the occurrence frequency of the error if the error is on the error frequency list, and adding the error to the temporary defect list if the error has an occurrence frequency greater than or equal to a threshold value established as a standard for classifying an error as a defect. The temporary defect list can be used as a final error list, and thereby reduce memory requirements.

Abstract: A sequencer overrun prevention method includes the steps of: initializing a sequencer; reading a timer value indicating when the sequencer begins operation; calculating a sequencer halting point by adding a predetermined time constant to the timer value; determining whether the sequencer operates at the sequencer halting point; and forcibly halting the sequencer when the sequencer operates at the sequencer halting point. The predetermined time constant is represented by T in the expression: T=(N)×(time required for one disk revolution)×(timer frequency), where N is indicative of a maximum number of detected indices and is greater than or equal to two. According to this method, the overhead time of a microprocessor can be reduced and sequencer overrun is prevented.

Abstract: A method for controlling a servo system of a hard disk drive of the present invention contemplates reading a servo defect list from a hard disk drive; performing a track seek order on a disk; ascertaining whether a corresponding servo is in the servo defect list; ignoring position information of the corresponding servo, when the corresponding servo is in the servo defect list; estimating position information of a track from position information of a servo immediately preceding the corresponding servo after ignoring the position information of the corresponding servo; performing a predetermined servo control algorithm after estimating the position information of the corresponding servo based on the position information of the servo immediately preceding the corresponding servo; and performing the servo control algorithm after reading out position information from the corresponding servo, when the corresponding servo is not in the servo defect list.