First and second read channel logic circuits are configured to process first and second signals communicated from respective first and second readers that simultaneously read from a magnetic disk. A first servo detection circuit generates a primary servo gate based on timing data from the first reader. The primary servo gate is used for processing the first signal via the first read channel logic. A second servo detection circuit that generates a secondary servo gate based on the primary servo gate and an adjustment value. The secondary servo gate is used for processing the second signal via the second read channel logic.

Systems, methods, devices, circuits for data processing, and more particularly to systems and methods for reporting a synchronization indication and for applying a synchronization window. As an example, a system is discussed that includes: a head assembly including a first read head and a second read head; a down track distance calculation circuit operable to calculate a down track distance between the first read head and the second read head; and a synchronization mark detection circuit. The synchronization mark detection circuit is operable to: assert a synchronization mark window based at a location based at least in part on the down track distance; query a first data set derived from the first read head for a synchronization mark occurring within the synchronization mark window; and query a second data set derived from the second read head for the synchronization mark occurring within the synchronization mark window.

According to one embodiment, a magnetic disk device includes a disk that has a track including a first servo sector and a second servo sector that is different from the first servo sector, a head that writes data to the disk and reads data from the disk, and a controller that records first signal strength record data related to a signal strength at which first target servo data that is a target of the first servo sector is read, and standardizes first signal strength data related to a signal strength at which the first target servo data is read when the first target servo data is read.

A magnetic disk apparatus according to an embodiment includes a magnetic disk, a magnetic head, a second memory, and a controller. On the magnetic disk, a servo sector where first servo data is recorded is provided. The magnetic head writes data and reads data to and from the magnetic disk. The first memory stores data to be written and stores data read from the magnetic disk. The second memory stores second servo data. The controller acquires the second servo data corresponding to the first servo data from the second memory based on the first servo data read by the magnetic head when passing over the servo sector. The controller executes positioning control of the magnetic head by using the first servo data and the second servo data.