Fay, Sharpe, Beall, Fagan, Minnich & McKee
Magnetic disk apparatus of constant-density recording type, magnetic disk used therefor and servo-writing device for patterning on the magnetic disk
 A constant-density type of magnetic disk apparatus is made up of a plurality of magnetic disks, wherein at least one of the surfaces of the magnetic disks is a servo face divided into a plurality of zones in the radial direction of the disks. A magnetic disk used in this apparatus and a servo-writing device for making this magnetic disk are also disclosed. In the magnetic disk apparatus and the magnetic disk, servo information regions and clock information regions are alternately provided on the servo face in the circumferential direction of the disks. The servo information regions are arranged radially with respect to the rotation center of the disks and each of the clock information regions includes a plurality of magnetic transitions representative of clocks, the number of which is different for each of the divided zones. A servo PLL circuit is provided to generate a servo clock signal on the basis of the signal reproduced from each of the servo information regions, and a write PLL is also provided to generate a write clock signal on the basis of the signal reproduced from each of the clock information regions. Also disclosed is a disk for use in a constant density-recording type magnetic disk apparatus, wherein a dummy track is provided along a zone boundary on the data face embedded with servo patterns of the disk. 
Hitachi, Ltd.
G G G G G G G
G11B G11B G11B G11B G11B G11B G11B
inventional inventional inventional additional inventional additional additional
Yosuke Toshiaki Hajime Makoto
Seo Tsuyoshi Aoi Saito