Browse Prior Art Database

Sector Obliteration

IP.com Disclosure Number: IPCOM000044436D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Collins, DW: AUTHOR [+2]

Abstract

Sector servoed disk drives provide servo information during a portion of each sector of rotation; however, when a defective servo sector is encountered, the defect or misinformation can lead to track misregistration or even prevent the drive from coming to a ready state on that track. To overcome this problem, defective sectors are overwritten to change the failing servo sector to a missing sector which is ignored by the system to prevent interference with the processing of either servo or data information. This technique is implemented by identifying the field to be permanently obliterated and rendering the field temporarily obliterated. This temporary obliteration is required to assure that the file will remain ready on a bad track.

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Sector Obliteration

Sector servoed disk drives provide servo information during a portion of each sector of rotation; however, when a defective servo sector is encountered, the defect or misinformation can lead to track misregistration or even prevent the drive from coming to a ready state on that track. To overcome this problem, defective sectors are overwritten to change the failing servo sector to a missing sector which is ignored by the system to prevent interference with the processing of either servo or data information. This technique is implemented by identifying the field to be permanently obliterated and rendering the field temporarily obliterated. This temporary obliteration is required to assure that the file will remain ready on a bad track. Temporary obliteration has been accomplished by injecting a high frequency signal (such as 5 MHz) into the load resistor of one of the automatic gain control (AGC) outputs to the detector only during the time the bad sector is passing. The file can now be asked to seek the bad track. The file will track follow since the bad sector is considered missing and the offtrack signal that it would generate is ignored. The bad sector is then permanently obliterated, the signal injected into the load resistor is removed, and the file proceeds to operate normally. The overwriting action used to facilitate obliteration can be effected using auxiliary circuitry or more easily, using a servo writer where the phase of the oblit...