Patent ID: 7006316

Claim:
A method of estimating a writer/reader gap in a disk drive, the disk drive comprising a disk having a first preamble and a first sync mark, and a head actuated over the disk, wherein the head comprises a writer separated from a reader by the writer/reader gap, the method comprising the steps of: (a) measuring a write delay during a first revolution of the disk by: reading the first preamble to synchronize cycling of a clock; reading and detecting the first sync mark; waiting a predetermined number of the clock cycles; writing a second preamble and a second sync mark on the disk; and counting a number of the clock cycles relative to when the first sync mark is detected and when the second sync mark is written; (b) measuring a read delay during a second revolution of the disk by: reading the first preamble to synchronize cycling of the clock; reading and detecting the first sync mark; waiting a predetermined number of the clock cycles; reading the second preamble to synchronize cycling of the clock; reading and detecting the second sync mark; and counting a number of the clock cycles relative to when the first sync mark is detected and when the second sync mark is detected; and (c) estimating the writer/reader gap in response to the measured write delay and the measured read delay.