Servo system for a magnetic disk memory having spiral tracks

摘要

Disclosed is a disk memory having a plurality of data sectors and servo sectors each provided between adjacent data sectors, spiral tracks being formed in each data sector and each servo sector. Servo information patterns are formed in each servo sector. To cause a read/write head to trace spiral tracks, the phases of the servo patterns with respect to servo tracks are sequentially displaced, from the first servo sector to the final m-th servo sector, by a value obtained by dividing the track pitch of the servo tracks by the number of servo sectors. In the m-th servo sector a servo index used for detecting that the servo sector is formed. A disk device is also disclosed which performs tracking control for the head along the spiral tracks.