US Patent 7974035 Timing recovery optimization using disk clock

Timing recovery optimization using disk clock. A novel means is presented to perform and provide control of the sampling frequency of a signal that is read from a disk within a hard disk drive (HDD). Two separate, yet somewhat cooperating control loops are employed to provide feedback control of the sampling frequency of the signal that is read from disk. A timing recovery loop and a disk clock loop operate in conjunction with one another according to some desired manner (which can be predetermined or adaptive) to ensure that the sampling of the signal is performed to a very accurate degree. In one implementation, the timing recovery loop governs the sampling rate until the disk clock loop has locked, from which time either the disk clock loop govern the sampling or some combination of the signals provided from the two loops govern the sampling.