Abstract: Embodiments of the present invention provide a magnetic disk device and a method for production thereof, the magnetic disk device being characterized in that the magnetic disk therein permits a plurality of tracks thereon to record correction data when necessary without decreasing its storage capacity. According to one embodiment, the magnetic disk device is characterized in that the magnetic disk has the first tracks and the second tracks formed thereon, the first tracks having servo data regions arranged cyclically, with a portion of a region between them being the correction data region and the remaining regions being the user data region, and the second tracks having the servo data regions arranged cyclically, with the region between them being the user data regions, and the multiprocessing unit (MPU) switches the servo extraction timing of the position information sampler depending on whether the track for servo reproduction by the magnetic head is the first track or the second track.

Abstract: Embodiments of the present invention provide a magnetic disk device and a method for production thereof, the magnetic disk device being characterized in that the magnetic disk therein permits a plurality of tracks thereon to record correction data when necessary without decreasing its storage capacity. According to one embodiment, the magnetic disk device is characterized in that the magnetic disk has the first tracks and the second tracks formed thereon, the first tracks having servo data regions arranged cyclically, with a portion of a region between them being the correction data region and the remaining regions being the user data region, and the second tracks having the servo data regions arranged cyclically, with the region between them being the user data regions, and the multiprocessing unit (MPU) switches the servo extraction timing of the position information sampler depending on whether the track for servo reproduction by the magnetic head is the first track or the second track.

Abstract: While executing a command that accesses a sector on a disk-shaped recording medium placed in a data recording device, an address of a sector where it is difficult to read data is recorded in a memory. After that, a determination is made as to whether or not the data recording device is executing a command. If it is judged that the data recording device is not executing a command, the address of the sector is read from the memory, and then a bad sector is searched for by detecting whether or not it is difficult to read data from each of surrounding sectors adjacent to the sector, the address of which has been read.

Abstract: A correction mechanism for use in a data storage system that allows data to be read even if the recorded data has been phase shifted.

Abstract: A servo system wherein a read head R detects a servo pattern that is written on a magnetic disk by a write head W. Position control of the write head W is exercised in accordance with the detected servo pattern, and the read head R detects a propagation pattern that is written on the magnetic disk by the write head W. Position of the write head W is corrected in accordance with the detected propagation pattern.

Abstract: In addition to the conventional test pattern writing in a center of each track and inspection of burst patterns (A and B patterns) through a writing test in a SAT, there is also performed a test pattern data writing test, which is done at each boundary between tracks. With this additional test, it is possible to accurately inspect both C and D burst patterns that are sensitive to a PES signal at each boundary between tracks.

Abstract: A mechanism to allow accurate control of the position of a magnetic head even if the state of the magnetic head has changed due to instability.

Abstract: While executing a command that accesses a sector on a disk-shaped recording medium placed in a data recording device, an address of a sector where it is difficult to read data is recorded in a memory. After that, a determination is made as to whether or not the data recording device is executing a command. If it is judged that the data recording device is not executing a command, the address of the sector is read from the memory, and then a bad sector is searched for by detecting whether or not it is difficult to read data from each of surrounding sectors adjacent to the sector, the address of which has been read.

Abstract: A servo system wherein a read head R detects a servo pattern that is written on a magnetic disk by a write head W. Position control of the write head W is exercised in accordance with the detected servo pattern, and the read head R detects a propagation pattern that is written on the magnetic disk by the write head W. Position of the write head W is corrected in accordance with the detected propagation pattern.

Abstract: A correction mechanism for use in a data storage system that allows data to be read even if the recorded data has been phase shifted.

Abstract: A mechanism to allow accurate control of the position of a magnetic head even if the state of the magnetic head has changed due to instability.

Abstract: In addition to the conventional test pattern writing in a center of each track and inspection of burst patterns (A and B patterns) through a writing test in a SAT, there is also performed a test pattern data writing test, which is done at each boundary between tracks. With this additional test, it is possible to accurately inspect both C and D burst patterns that are sensitive to a PES signal at each boundary between tracks.

Abstract: A hard disk drive (HDD) having a control unit that reduces the number of control signals required to control the operation of the channel and amplifier. The HDD includes a control unit for controlling reading or writing data from or to a magnetic head, a preamplifier for amplifying the data from the magnetic head, and a channel module which is controlled by the control unit. The channel module converts digital data signals to data write signals and also converts analog signals from the preamplifier to digital signals. Control information is transmitted to the channel module over the data bus which is used to transmit or receive data read/write signals. The channel module performs control in response to transmitted control information.

Abstract: A system for preventing off track data write operations in data storage devices such as hard disk drives. In a preferred embodiment, the amplitude of a head output signal is monitored. The output signal amplitude value is determined by measuring the voltage of a capacitor used in a Variable Gain Amplifier (VGA) in an Automatic Gain Control (AGC) circuit of a hard disk drive channel unit. The measured head output signal amplitude is compared with a previously determined minimum normal head output signal amplitude reference value to determine whether the head output signal amplitude is within a normal operating range. If the measured value is less than the reference value then the head is in an off track position, and the data write operation is inhibited. Radial position dependent amplitude reference values can also be used.

Abstract: A method and system are disclosed for controlling the application of a reset voltage pulse to a GMR sensor in a direct-access storage device (DASD), such that existing data is not damaged or altered. Each sensor is positioned or parked at a location reserved for reset pulse application, where no valid data is stored. A complex interrelated set of commands is then initiated, and upon completion of the entire set of interrelated commands, a reset pulse is applied to the GMR sensor. Any variation or interruption in the complex interrelated set of commands will result in a disarming of the reset pulse circuitry, effectively preventing an accidental or inadvertent application of the GMR reset pulse. Alternately, a group of GMR sensors each may be tracked to a reserve track, forming a reserve cylinder. Servo marks on the reserve track are sensed by a selected sensor and utilized to ensure no valid data is present.

Abstract: The present invention relates to a testing method and tester which reliably flags errors in disk drives, thereby reducing disk failures. In the testing method and tester, a random error due to noise occurs anywhere in a sector (read)/cylinder (write), whereas a repeatable error occurs in a specific area on a disk. If a plurality of random errors occur in the same sector or cylinder, no flagging is performed if the occurrence positions are distant from each other.

Abstract: A disk and a disk drive having a servo start mark for identifying a servo-information start position recorded on the disk is provided. The servo start mark has a plurality of bit patterns unused for other areas in servo information. A method for identifying the position of a signal transducer on a disk is also provided in which it is judged that the signal transducer is present at a predetermined position even if an error is present and the error is a one-bit error. This is accomplished by assuming that the position is correct when the following conditions are confirmed: (a) a parity error occurs in a read servo-information bit pattern and (b) read servo-information bit pattern does not coincide with servo information of an adjacent track.