Abstract: A method of writing servo data onto a disk is disclosed. A spindle motor spins the disk, and a back electromotive force (BEMF) signal is measured from the spindle motor. A repeatable phase error (RPE) is extracted from the BEMF signal to generate an adjusted BEMF signal. A servo write clock is synchronized in response to the adjusted BEMF signal, and the servo data is written to the disk using the servo write clock. In one embodiment, the servo data comprises spiral seed patterns that are processed to write concentric servo sectors to the disk.

Abstract: A method of writing spiral tracks for a disk drive is disclosed. A first concentric reference track is written at a first radial location near an outer diameter of a disk surface, a second concentric reference track is written at a second radial location near an inner diameter of the disk surface, and a third concentric reference track is written at a third radial location between the first and second radial locations. Prior to writing one of the spiral tracks, the concentric reference tracks are read to generate position error signals used to adjust a velocity profile for writing the spiral tracks. The velocity profile is adjusted to compensate for linear and non-linear disturbances due, for example, to thermal expansion.

Abstract: An apparatus and method for testing a variety of hard disk drives is disclosed. The apparatus includes a computer connected to a control board and an interface board. The interface board is connected to a testing board. The hard disk drive is connected to the control board and testing board. The hard disk is tested by first erasing a track of data bits at full write current in one direction or polarity and second erasing the track at minimal write current in the opposite direction. The track is read and compared to a predetermined threshold and any level exceeding the threshold is considered defective.