Abstract: The present invention relates to a system for determining whether the flying height of a read/write head above a disk in a disk drive is within an acceptable range, in substantially real time. The system relies on variations in read signal resolution with flying height to make the determination. In one embodiment, read signal resolution is measured and compared to a predetermined threshold value to determine whether the present flying height is in the desired range. In another embodiment, the number of peaks in a read signal that are detected (and/or not detected) by a detector is used to determine whether the head is in the proper flying height range. Because of read signal resolution effects, the number of detected peaks will decrease as the flying height of the head is increased. The system also provides for postponing a transfer of data to/from the disk when it is determined that the head is not within the acceptable range.

Abstract: The present invention provides a method and apparatus for assuring that the desired data is transferred between a variable rate disk drive and a host system during read and write operations. The invention involves retaining a variable amount of data in a buffer memory after the data has been transferred between the buffer memory and a magnetic disk with the variable amount of data retained based upon a predetermined fixed period of time associated with error conditions and a disk transfer rate. If an error condition is detected during a transfer of data between the buffer memory and the disk, all of the retained data may be retransferred after the error condition has been corrected.