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DASD Recording Sub-System Parameter Optimization by Head Radius

IP.com Disclosure Number: IPCOM000101345D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 78K

Publishing Venue

IBM

Related People

O'Dowd, NP: AUTHOR [+2]

Abstract

Disclosed is a method for use in disk files (DASD) to optimize write current, precompensation and PRML equalization for each head and track radius by storing a table of optimization parameters on a reserved area of the disk to be read by the file microprocessor at power on, thus minimizing soft error rates.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

DASD Recording Sub-System Parameter Optimization by Head Radius

       Disclosed is a method for use in disk files (DASD) to
optimize write current, precompensation and PRML equalization for
each head and track radius by storing a table of optimization
parameters on a reserved area of the disk to be read by the file
microprocessor at power on, thus minimizing soft error rates.

      In a recording sub-system for a disk file, there are three
programmable parameters:  Write Current, Write Precompensation and
Read Equalization.  The Read Equalization value can optionally be put
into an adaptive mode, where it uses the first few bytes of a record
to fine-tune a filter.  Otherwise, all these values are loaded into
registers by the File Control Microprocessor. Traditionally, there
has been a "Reduce Write Current Cylinder" and an "Enable
Precompensation Cylinder", such that data operations at smaller radii
than this cylinder will have reduced write current, and
precompensation enabled.  This misses an opportunity for adjusting
the programmable parameters individually by head and radius, in an
effort to reduce the soft data handling error rate of the DASD.

      An automatic technique for use in manufacturing DASD can
generate tables for the above three parameters against head and
radius.  The tables are written on a reserved region of the DASD and
are subsequently used by the File Control Microprocessor when it is
performing data operations.  Each part of the technique involves
measuring the voltage waveform from the head, comparing it with the
ideal voltage waveform, and adjusting the parameter in question until
the overall difference between the measured and ideal waveforms is
minimized.  The measurement requires the signal at entry to the
channel to be digitized and reported to a test system.  This may be
done using a digitizer in the channel and an external logic analyzer,
or other combinations of test equipment appropriate to the DASD
design.

      Write Current Optimization The track of interest is written
with random data. This is then overwritten with the reference
pattern.  Next, the adjacent tracks are written with random data.
Finally, the track of interest is read for comparison with the ideal
response.

      Write Precompensation Optimization The track of interest is
written with the reference pattern, and read for comparison with the
ideal response. This is repeated for various values of write
p...