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STT8000A Product Manual Page 67

Write equalization

The drive uses the technique of write equalization. RLL encoding has a 4:1 ratio in

the minimum and maximum spacing between flux transitions. 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 900 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.

Randomization

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.

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Seagate STT8000A Manual Page 75