MAGNETIC DISK DEVICE AND DISK SUB-SYSTEM

PURPOSE:To obtain a magnetic disk device and a disk sub-system capable of preventing a magnetic head and the magnetic disk from being damaged by detecting the floating abnormality of the magnetic head including the floating attitude thereof. CONSTITUTION:The gain information of a read amplifier at the time when data for measurement are reproduced is stored in an AGC control memory circuit 21 beforehand, and by reproducing the data for measurement by using this gain information, the reproduced data varying only by the floating height and attitude of the head are obtained. The variation of voltage amplitude of these reproduced data is detected by an envelope signal producing circuit 16, and also the variation of phase difference of a read out period of the reproduced data against a reference period is detected by a phase difference signal producing circuit 17. By using these variations, the floating interval and attitude variation of the magnetic head are calculated by a computer 18 and when the floating interval and attitude variation of the magnetic head exceed the allowable ranges, a warning, etc., are given to the user, thereby the magnetic head and the magnetic disk are prevented from being damaged.