Abstract: A hard disk drive system includes a first channel module and a second channel module. The first channel module is configured to receive a first data from or transfer the first data to a first amplifier module of a hard disk assembly when reading from or writing to a first surface of a disk of the hard disk assembly. The second channel module is configured to receive a second data from or transfer the second data to a second amplifier module of the hard disk assembly when reading or writing to a second surface of the disk while the first channel module receives the first data from or transfers the first data to the first amplifier module.

Abstract: Servo patterns for patterned media. The servo pattern includes specification of cylinder/track ID with and without a Gray code. The servo pattern space is minimized by the optimum usage of the islands. This is achieved by island allocation rules to take advantage of non-magnetic island. The island allocation also provides for easier lift-off. Logic is used to encode and decode the Gray code. Further, the Gray code is designed to stabilize the magnetic island/non-magnetic island ratio to allow for easier manufacture.

Abstract: A system for grading defective bit patterned magnetic media by disk sector in hard disk drives recovers a portion of any defective sectors at a lower areal density. The invention reduces the track pitch density for sectors containing amalgamated islands while leaving the remainder of the defect-free sectors in the zone optimized for linear bit density. This recovers a portion of the defective sector, approximately in proportion to the ratio of amalgamated islands over the original number of islands. A typical zone is first optimized for tracks per inch during formatting of the patterned media disk drive. The zone is then broken up into sectors that can each be optimized separately for linear bit density to ensure the maximum sustainable capacity for each sector.

Abstract: Provided is an optical disk reproducing device for controlling false detection of synchronization signals due to intersymbol interference, and stably improving accuracy of frequency acquisition of a PLL even when offset and so on occur. A signal width close to an original mark length is obtained to use for frequency acquisition of the PLL by, for example, using two different slice thresholds and taking a width between a rising of a result of slicing at one threshold and a falling of a result of slicing at the other threshold as a synchronization signal width. When asymmetric properties due to offset, asymmetry, etc. occur, an amount of corrections on the slice threshold is calculated, and it is reflected on a threshold previously set to always obtain a correct synchronization signal width.