Abstract: A data storage system includes an encoder subsystem comprising an error correction code encoder, a modulation encoder, and a precoder, and a decoder subsystem similarly comprising a detector, an inverse precoder, a channel decoder, and an error correction code decoder. The error correction encoder applies an error correction code to the incoming user bit stream, and the modulation encoder applies so-called modulation or constrained coding to the error correction coded bit stream. The precoder applies so-called precoding to the modulation encoded bit stream. However, this precoding is applied to selected portions of the bit stream only. There can also be a permutation step where the bit sequence is permuted after the modulation encoder before precoding is applied by the precoder. The decoder subsystem operates in the inverse manner.

Abstract: An apparatus for providing dynamic equalizer optimization is disclosed. The present invention solves the above-described problems by providing equalizer coefficient updates that converge towards the same solution as the direct method without having to first write a known pattern to the disk or requiring any prior knowledge of the data already written on the disk. The adaptive cosine function may be used to modify only a DFIR tap set, only the j and k parameters of a cosine equalizer or to modify both the tap set for a DFIR filter and the j and k parameters of the cosine equalizer. Another algorithm, such as the LMS algorithm, may be used to modify parameters not modified by the cosine algorithm.

Abstract: The linear range of a servo system for a magnetic storage device using a compared amplitude burst servo pattern and a magneto resistive (MR) sensor is enhanced by reversing the bias current. With the servo bursts displaced to opposite sides of the track centerline, the bias current is reversed to have the read function occur when the sensor is electrically biased to present the higher gain, more uniform end portion of the readback sensitivity profile at the side of the track at which the burst is written. Reversing the bias current in an MR sensor causes the readback sensitivity profile to be mirrored about the sensor center enabling the more uniform portion of the sensor response to be used to sense the respective servo pattern bursts. Where differences occur in MR gain between bias current directions, normalization or other correction is provided to compensate for variation in sensor gain.

Abstract: Disclosed is a method for recovering data from a portion of a magnetic surface that contained a read error. After a read error is encountered a magnetic transducer undergoes a head state change. The head state change is accomplished by either writing to a reserve area of the magnetic surface and or reading a portion of the magnetic surface and then rewriting to that portion of the magnetic surface. After the magnetic transducer undergoes a head state change, the portion of the magnetic surface that contained the read error is reread.