Provided are a bit flipping device and method and a computer readable program for the same. The bit flipping device for input data having a two-dimensional array pattern includes: a clustering unit configured to generate at least one input data sequence based on the two-dimensional array pattern of the input data and classify the input data sequence into at least one cluster according to a preset method; and a bit flipping unit configured to perform bit flipping on erroneous bits in the input data sequence based on the classified cluster. Therefore, it is possible to further reduce inefficiency while further reducing system complexity compared to the existing error correction code-based bit flipping method by coupling the bit flipping device to an output side of a partial response maximum likelihood (PRML) detector to classify an output value of the PRML detector into at least one cluster and perform bit flipping based on the classified result.

According to one embodiment, a magnetic disk device includes a disk including a zone servo boundary area including a first area of a first servo frequency, a second area of a second servo frequency, and a third area of the first servo frequency, in a servo area, a head, and a controller demodulating first servo data of the first area to derive a position of the head and demodulating first corrected data of the third area to correct the position of the head. The first area, the second area, and the third area are aligned in order in a traveling direction. The first area and the second area are adjacent to each other in a circumferential direction of the disk. The second area and the third area are adjacent to each other in the circumferential direction.

According to an embodiment, a magnetic disk has a plurality of second servo sectors and a plurality of third servo sectors each arranged between two second servo sectors of the plurality of second servo sectors, in which the second and third servo sectors are arranged in a circumferential direction. A controller performs a first demodulation for detecting a servo mark and demodulating a burst pattern on the servo data in each second servo sector. The controller performs a second demodulation for demodulating the burst pattern without detecting the servo mark, on the servo data in each third servo sector. The controller performs the second demodulation on the servo data in a fourth servo sector which is one of the plurality of second servo sectors in a case where the detection of the servo mark fails when the first demodulation is performed on the servo data in the fourth servo sector.

A data object has a lock and a condition indicator associated with it. Based at least partly on detecting a first setting of the condition indicator, a reader stores an indication that the reader has obtained read access to the data object in an element of a readers structure and reads the data object without acquiring the lock. A writer detects the first setting and replaces it with a second setting, indicating that the lock is to be acquired by readers before reading the data object. Prior to performing a write on the data object, the writer verifies that one or more elements of the readers structure have been cleared.

A data object has a lock and a condition indicator associated with it. Based at least partly on detecting a first setting of the condition indicator, a reader stores an indication that the reader has obtained read access to the data object in an element of a readers structure and reads the data object without acquiring the lock. A writer detects the first setting and replaces it with a second setting, indicating that the lock is to be acquired by readers before reading the data object. Prior to performing a write on the data object, the writer verifies that one or more elements of the readers structure have been cleared.

Example systems, read channel circuits, data storage devices, and methods to provide signal correction based on soft information in a read channel are described. The read channel circuit includes a soft output detector, such as a soft output Viterbi algorithm (SOVA) detector, and a signal correction circuit. The soft output detector passes detected data bits and corresponding soft information to the signal correction circuit. The signal correction circuit uses the soft information to determine a signal correction value, which is combined with input signal to return a corrected signal to the soft output detector for a next iteration. In some configurations, the signal correction value may compensate for DC offset, AC coupling poles, and/or signal asymmetries to reduce baseline wander in the read channel.

According to one embodiment, a magnetic disk device includes a disk including two first servo sectors and at least a second servo sector, a head, and a controller, wherein the first servo sector includes burst data and a first data pattern written before the circumferential direction of the burst data, the second servo sector includes the burst data, the first data pattern, and a second data pattern written after the circumferential direction of the burst data, a first frequency of the first data pattern is different from a second frequency of the second data pattern, and a first length of the first data pattern is different from a second length of the second data pattern.

A technique includes in a data storage device, sensing a plurality of data streams from a track of storage media as the media moves in a given direction using a plurality of read elements such that at least one of the read elements is redundant. The technique includes combining the data streams to generate a data stream indicating data read from the track.

The invention provides a signal processing device, including: an extraction section that extracts, from an input digital signal, a decoding target signal at an extraction timing that has been determined as a timing for extracting the decoding target signal; a decoding section that decodes the decoding target signal by estimating, by a maximum likelihood decoding, a candidate for a decoding result of the decoding target signal extracted by the extraction section and detecting a maximum likelihood decoding result; and an adjustment section that adjusts the extraction timing using a likelihood of the candidate for the decoding result estimated by the decoding section.

According to one embodiment, a magnetic recording and reproducing device includes a magnetic recording medium, a magnetic head, and a processor. The magnetic head includes a first reproducing element portion and a second reproducing element portion. The processor is configured to acquire a first signal and a second signal, and to output an output signal according to either one of the first signal and the second signal. The first signal is obtained by reproducing information recorded on a first recording region by the first reproducing element portion. The second signal is obtained by reproducing the information recorded on the first recording region by the second reproducing element portion.