Browse Prior Art Database

Disc File Defect Screening System

IP.com Disclosure Number: IPCOM000081672D
Original Publication Date: 1974-Jul-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 64K

Publishing Venue

IBM

Related People

Hanson, CC: AUTHOR [+2]

Abstract

This defect screening system allows a magnetic disc 20 to have a single-defect site on any data track, for example defect sites 22a and 24a on data tracks 22 and 24, and still have the track useable. A defect on the magnetic media surface of a magnetic disc is defined as an area on a data track, where the magnetic read-back signal amplitude modulates to a level below a certain percentage of the average signal level on the particular track. The defect screening system, in accomplishing this result, provides essentially a floating-index period and is applicable to formatted disc applications. The production test and formatting technique is as follows: 1) Analog test the track for defects (either missing bits, modulation, or extra bits).

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 54% of the total text.

Page 1 of 3

Disc File Defect Screening System

This defect screening system allows a magnetic disc 20 to have a single-defect site on any data track, for example defect sites 22a and 24a on data tracks 22 and 24, and still have the track useable. A defect on the magnetic media surface of a magnetic disc is defined as an area on a data track, where the magnetic read-back signal amplitude modulates to a level below a certain percentage of the average signal level on the particular track. The defect screening system, in accomplishing this result, provides essentially a floating-index period and is applicable to formatted disc applications.

The production test and formatting technique is as follows:
1) Analog test the track for defects (either missing bits,

modulation, or extra bits).
2) If no defect is found, format the disc relative to the

optical index or the normal format reference whatever that

may be.
3) When a defect is found, store the coordinates of the location

by some means and test the remainder of the track.
4) If no more than one defect is detected on the track, its

location can be used as a reference for index.
5) Format the disc relative to the defect, allowing sufficient

tolerance on either side of the defect to avoid writing over

it.

When the read/write head 26 has been positioned on the data track being considered and the magnetic test signal has been written, the testing and formatting will be controlled by the system shown in the diagram: and the timing chart shows the sequence of events that takes place on a track containing a single-defect area. The diagram shows the test system required to format disc 20 such that a single defect, such as defect 22a, can be allowed on a track, such as track
22. The sequence of performing the test is as follows for the first revolution:
1. Assume the test pattern has been written on the disc.
2. Energize defect test circuit 25 and monitor the signal from

head 2b for a complete r...