Patent ID: 7929233

Claim:
A method of grading defective bit patterned magnetic media by disk sector in a hard disk drive, comprising: (a) providing a disk with bit patterned magnetic media having tracks of bits that are divided into sectors; (b) determining if any of the sectors have tracks that are not concentric such that the bits on adjacent ones of the tracks are amalgamated; (c) designating sectors having amalgamated bits as “defective;” and (d) recovering a portion of the defective sectors such that the defective sectors have an areal density that is lower than an areal density of other ones of the sectors; and steps (b)-(d) comprise writing “l′s” to all bits on odd tracks, counting A=M tracks×N bits; writing a “0” to all bits on even tracks; reading each bit on odd tracks, counting B=M tracks×N bits; determining whether “A=B”; if A=B, proceeding to coding; and, if A≠B, optimizing amalgamated sectors for areal density.