Browse Prior Art Database

Spiral Track Disk Format for Continuous Data Rate

IP.com Disclosure Number: IPCOM000105847D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Barnett, B: AUTHOR [+3]

Abstract

Disk drives with spiral tracks can be used to get a continuous stream of data as may be required for multimedia video applications. In this method for allowing continuous data flow from the disk drive, odd-numbered heads spiral inward and all even-numbered heads spiral outward as the disk turns. Continuous data flow is interrupted only by switches between heads. The issue is how to write the position-sensing pattern.

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Spiral Track Disk Format for Continuous Data Rate

      Disk drives with spiral tracks can be used to get a continuous
stream of data as may be required for multimedia video applications.
In this method for allowing continuous data flow from the disk drive,
odd-numbered heads spiral inward and all even-numbered heads spiral
outward as the disk turns.  Continuous data flow is interrupted only
by switches between heads.  The issue is how to write the
position-sensing pattern.

      The key features of position-sensing patterns is that they
produce an integral number of samples per revolution of the disk.
Further the position-sensing signals for the two directions of spiral
motion are recorded on a separate disk surface using a separate head.
It is required here that there be an even number of patterns of
samples per revolution.  Then all even-and odd-numbered samples to a
radial line called the index are written so that they spiral inward
and outward by one track per revolution, respectively.

      The writing of the position-sensing pattern is illustrated
using a three-part pattern consisting of a synchronization mark C
followed by a second mark A shifted toward the OD and a third mark B
shifted toward the ID.  The A and B marks have a shape such that the
readback signal generated from the mark changes more or less linearly
in amplitude as the readback head moves radially from the track
center.  The position error signal is (A-B)/C.  Clearly the sign of
the position error signal changes from track to trac...