Magnetic disk device with dummy write function

摘要

A magnetic disk device of embedded-servo type capable of performing dummy operation for suppressing waveform degradation of signal reproduced by magnetic heads at a high speed with high reliability. When a waveform deformation occurs in a No.0 head (11), a controller (1) changes over the No.0 head (11) to a No.1 head (12) operating normally, whereupon a cylinder portion for which dummy operation is to be performed is sought on the basis of the servo information supplied from the No.1 head (12). The cylinder portion destined for the dummy write operation contains servo information at timing positions same for the individual magnetic heads. When passing of the No.1 head (12) over the cylinder portion is confirmed, the No.1 head (12) is changed over to the No.0 head (11) for performing dummy write operation for suppressing the waveform deformation of the reproduce signal outputted from the No.0 head (11). Before the timing for succeeding information (2), the No.1 head (12) is restored by issuing a head change command signal (6). Because the seek operation is realized exclusively by the magnetic head suffering no abnormality, the dummy write operation for preventing waveform deformation of the reproduced signal outputted from the No.0 head (11) can be realized without fail.