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Browse Prior Art Database

Logical Index Skew for Full Revolution Surface Analysis Test (SAT) Rotating Memory Devices

IP.com Disclosure Number: IPCOM000122084D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 48K

Publishing Venue

IBM

Related People

Cummings, PA: AUTHOR [+4]

Abstract

Described is a method of providing 100 percent Surface Analysis Test (SAT) coverage for each track of data located in a Rotating Memory Device.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 91% of the total text.

Logical Index Skew for Full Revolution Surface Analysis Test (SAT)
Rotating Memory Devices

      Described is a method of providing 100 percent Surface Analysis
Test (SAT) coverage for each track of data located in a Rotating
Memory Device.

      The SAT is a necessary step for marking defective areas on the
customer data disks within a DASD device.  This invention allows for
the SAT process to identify 100 percent of the disk defects through
hardware control of placing the Logical Index Pulse.

      As seen in the figure, there is an area adjacent to the Sector
and Index pulses which cannot be SATed.  Also shown in the figure is
the ability to shift Index, and thus all Sector pulses, by an amount
greater than the area which cannot be SATed.  This allows the
Micro-Processor to gather error information on all of the byte
locations within the DASD.

      The implementation of this invention consists of operating the
file in either the normal or skewed mode for placement of the Logical
Index.  After all of the faulty byte locations are recorded in one
mode, the Logical Index is offset to the opposite mode (which is a
known amount of byte shift), and the new locations of byte faults are
recorded and translated to their actual placement from the normal
Logical Index location.

      In conclusion, this invention allows for a 100 percent SAT
coverage using the file electronics, as compared to Analog SAT which
required special test-fixtures and still did...