Write Equalization; Randomization - Seagate STT20000A Product Manual

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Write equalization

Randomization

STT20000A Product Manual
The drive uses the technique of write equalization. Write equalization inserts short
pulses in the write current to break up the long spacing intervals. These pulses are
too short to be detected in the read process but result in significant improvement in
read-back resolution.
On 1650-Oersted media, write equalization provides the benefit of compatibility with
Magneto-Resistive (MR) heads. MR heads are prone to saturation by low frequency
flux with high energy content. Equalization redistributes this energy to higher
frequencies and eliminates the problem.
To reduce problems resulting from long strings of repetitive data with a bad peak
shift or amplitude characteristics, a data randomizer algorithm is used on all bytes in
the data and control area of each block. This randomizing takes place prior to the
encoding of the data.
Chapter 6
Page 69