Digital Equipment Corporation

Samuel B Skraly

John Edward DeRoo

Robert C Frame

Bernardo Rub

Anne Solli

A data processing system records information on magnetic disks in a format in which sector headers, which include embedded servo information, are radially aligned and recorded at a single frequency and data are recorded at various band-related frequencies. The system records sector headers at a frequency which is optimal for the recording of address information in the shortest sector and records the data at frequencies which are optimal for the recording of information in the disk space allocated to the data portion of the various lengths of sectors. The system synchronizes to the headers, using conventional embedded servo synchronization methods, and produces header timing signals. It can then use the same header timing signals to locate and interpret the headers on different tracks, since the header frequency and the location of the headers are the same in every track. The system may record the data portions of the sectors at frequencies which are related to the header frequency by ratios of small integers. The system then uses, in synchronizing to the disk, a phase locked loop which includes a voltage controlled oscillator (VCO) that is driven to a reference frequency which is directly related to the header frequency. The system divides-down the frequency of the VCO output signal to produce the timing signals for the header. Also, it uses a version of the output signal of the VCO, which is divided-down by a band-related value, as a timing signal for the data.

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Westboro, MA, United States of America

Samuel B Skraly