Patent ID: 7486461

Claim:
A magnetic disk device comprising: a magnetic disk to store servo data and record/reproduce user data; a magnetic head to read the servo data and read/write the user data; a disk control unit which predicts the variation of the servo sector pulse interval indicating the timing of the servo data read by the magnetic head and sets an optimal variation of the data sector pulse interval which prescribes the user data read/write timing for the servo sector pulse interval; and a disk controller which generates data sector pulses based on the set optimal variation of the data sector pulse interval and outputs the data sector pulses to the magnetic head, wherein the optimal variation of the data sector pulse interval is set based on a predicted variation of the servo sector pulse interval, wherein the disk control unit is configured to detect an interrupt from a servo control unit of the disk controller at an edged transition of a servo sector pulse, refer to register information in a data sector pulse generation control register block of the disk controller and learn the servo sector pulse interval,—obtain a variation from a previously stored standard value by comparing the learnt servo sector pulse interval with the standard value, and predict the variation of the next servo sector pulse based on the variations obtained for a number of preceding servo sector pulses.