Seagate STT8000A - Manual (Page 75)

Tape format Chapter 6
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.