Patent ID: 8619380

Claim:
A method comprising: while writing a servo pattern on a machine readable medium rotating about a spindle, i) recording, over time, a plurality of time stamps associated with a characteristic of a back electromotive force signal generated as the machine readable medium rotates about the spindle, wherein the characteristic of the back electromotive force signal repeats over the time that the plurality of time stamps are recorded, and wherein the characteristic of the back electromotive force signal is expected to repeat at expected times over the time that the plurality of time stamps are recorded, ii) performing a comparison of one or more of the plurality of time stamps with one or more of the expected times that the characteristic of the back electromotive force signal is expected to repeat, iii) based upon the comparison, detecting a timing error associated with writing the servo pattern on the machine readable medium, and iv) based on the timing error, re-writing at least a part of the servo pattern that was previously written on the machine readable medium.