Abstract: The present invention is directed to a method and apparatus for detecting and monitoring a bi-state head when self-servowriting a disk drive. In one embodiment, an integration window is opened about an expected time that a read head will read spiral servo information. An integration value associated with the integration window is determined. Next, a determination is made as to whether the integration value is less than a predetermined low amplitude limit. If it is, a comparison is made between a location of a maximum sync frame of a read signal envelope in the integration window and the center of the integration window. The read head is identified as a bi-state head if the location of the maximum sync frame is greater than a predetermined off-center limit relative to the location of the center of the integration window.

Abstract: A media noise optimized (MNO) detector for a read channel compensates for pattern dependent media noise, and compensates for nonlinearities from many sources such as residual MR nonlinearity, residual nonlinear transition shift, partial erasure, write-induced nonlinearity, and steady-state mis-equalization. The MNO detector is implemented by adjusting a conventional Viterbi detector branch metric so that the channel output value (ideal value) can be a nonlinear function of the state/branch bits, and the branch metric scaling factor is a function of the state/branch. For a given state/branch, the ideal value is the mean of analog-to-digital converter samples for the pattern corresponding to the state/branch, and the branch metric scaling factor is proportional to the noise variance for the pattern corresponding to that state/branch.

Abstract: A method of determining side track erasure in a disk drive having a disk and a transducer. A target track and one or more side tracks proximate to the target track on the disk are selected, and recording parameters for recording signals on the target track and each side track with the transducer are selected. Thereafter, signals are recorded on each side track and then signals are recorded on the target track multiple times. A reduction in the integrity of the recorded signals on each side track due to recording signals on the target track multiple times is detected, and the detected reduction in the integrity of the recorded signals on each side track represents the amount of the erasure of the recorded signals on the side track. Recording parameters are changed based on the signal integrity reduction to minimize side track erasure.

Abstract: Detecting flaws in a disk drive includes sampling a read signal provided by reading a data pattern from a disk to obtain samples, obtaining significant samples from the samples, deriving a value from the significant samples, and reporting a flaw if a comparison between the derived value and a threshold value is unacceptable.

Abstract: A method and apparatus for writing spiral servo information onto one or more disk surfaces at a variable velocity using a servo track writer (STW) is provided. In one embodiment, a variable velocity profile is chosen so that spiral crossing angles across the disk surface are set to be equal. In another embodiment, a variable velocity profile is chosen so that spiral crossing angles across groups of tracks (i.e., two or more tracks) are set to be equal. In yet another embodiment, a variable velocity profile is chosen to adjust the number of tracks per inch (TPI) across the disk surface.

Abstract: A method for determining embedded runout correction (ERC) values using iteration and variable gain in a disk drive. A disk has a track written thereon, an ERC value is determined for a servo sector on the track using variable gain, and the variable gain decreases based on the number of revolutions of the disk.

Abstract: A disk drive detects head touchdown based on a magnitude of a position error signal at a discrete frequency. The discrete frequency is one-half the disk rotation frequency or an integral multiple of the disk rotation frequency. The head is heated by turning on a heater at the discrete frequency, thereby injecting bias into a servo system that increases the PES magnitude. In addition, the servo system has a first transfer function for tracking the head during read and write operations and a second transfer function for tracking the head during head touchdown detection. The second transfer function has smaller vibration rejection than the first transfer function so that the disk drive is less sensitive to vibration during read and write operations than during head touchdown detection.

Abstract: Dynamically detecting off-track errors in a disk drive by adjusting transducer head position control parameters in response to shock events. In an embodiment, shock events with large magnitude trigger a severe shock timer which lengthens the write fault before write operations resume. In another embodiment, a lower shock threshold is used following an initial shock event. In yet another embodiment, a lower shock threshold is used if an accumulated average position error of the transducer head is large.

Abstract: The present invention is directed to a method and apparatus for improving spiral-based position correction system stability via kernel frequency component modification. In one embodiment, a disk drive includes a disk surface with servo information written thereon, wherein the servo information includes repeatable runout. The disk drive includes a servo system having an error transfer function. Frequencies, where the error transfer function may experience phase changes, are determined and the direction of such phase changes are also determined. A kernel, which is used to calculate position correction values to compensate for repeatable runout, is provided. Phases of frequency components in the kernel, which correspond to the frequencies where the error transfer function may experience phase changes, are rotated.

Abstract: A system and method for caching and managing data streams from a storage media is disclosed. The system includes a plurality of virtual buffers for a plurality of data streams. Each data stream correlates to a virtual buffer. The system also includes a cache memory to store the plurality of virtual buffers. The system also includes a stream manager to assign the plurality of data streams to the plurality of virtual buffers.

Abstract: A method and apparatus for writing spiral servo information is provided. In one embodiment, a servo track writer having a digital signal processor is provided. The servo track writer also includes a clock head, which reads a clock track from a disk surface to generate a clock signal that is used to provide interrupt signals to the digital signal processor. A transducer, which writes spiral servo information onto the disk surface, is positioned under control of the digital signal processor based upon the interrupt signals. In one embodiment, a method of writing spiral servo information onto a disk surface using a servo track writer having a digital signal processor is provided. The method includes the steps of reading a clock track written onto the disk surface to generate interrupt signals; providing the interrupt signals to the digital signal processor; and, positioning a transducer over the disk surface under control of the digital signal processor based upon the interrupt signals provided thereto.

Abstract: The present invention is directed to a method and apparatus for providing multi-point position demodulation of a read head when using spiral-written servo information. In one embodiment, a disk surface has spiral servo information written thereon. A read head generates a read signal envelope when reading the spiral servo information. A read signal envelope is detected within an integration window and integration values are accumulated over the integration window. The accumulated integration values are multiplied by a first number associated with a first integrator value and a second number associated with a second integrator value. A first position error signal associated with the first integrator value is determined, and a second position error signal associated with the second integrator value is also determined. A final position error signal is determined using the first position error signal and the second position error signal.

Abstract: A method and apparatus for generating high quality real random numbers is provided. In particular, the present invention enables a hard disk drive of a computer to function as a generator of high quality real random numbers by monitoring one or more of a disk drive's parameters, wherein such parameters are subjected to environmental effects. The system of the present invention does not require the addition of any hardware not normally associated with a computer. According to one embodiment of the present invention, a parameter of the disk drive is monitored, and after processing and filtering the parameter is provided to an application as a random number. Monitored parameters may include the position error signal of a transducer head with respect to a track, temperature, channel gain, transducer head flying height, etc. According to one embodiment of the present invention, the various other parameters may be combined or used in concert to provide high quality real random numbers.

Abstract: Methods and apparatuses for writing spiral servo patterns on a disk surface are disclosed. In one embodiment, a method is provided to write servo information onto a disk surface in spiral patterns in a non-sequential manner. In another embodiment, a thermal warm-up regimen is performed prior to writing spiral patterns onto the disk surface. In another embodiment, a reference track is used to position a write head when writing spiral patterns onto the disk surface. By using one or more of the above embodiments, the affects of thermal and/or mechanical changes may be reduced when writing spiral patterns.

Abstract: A disk drive includes recording media having one or more recording surfaces, one or more transducer heads positionable relative to the recording surfaces by an actuator operating within a head position servo loop, and a data transfer driver. A preamplifier in the data transfer driver includes one or more head interfaces, each head interface for controlling a transducer head for read and write operations, and a mode controller for controlling each head interface based on configuration information for selectively (i) reading data from at least one recording surface, (ii) writing data to at least one recording surface, and (iii) simultaneously reading data (such as a reference pattern) from at least one recording surface and writing data (such as servo patterns) to at least one recording surface.

Abstract: A method and apparatus for overwriting data in a disk drive is provided. In one embodiment, a disk drive includes a disk surface and a write head associated therewith. The disk surface has servo information and user data written thereon. The user data is written by the write head. User data is overwritten by sweeping the write head from a first radius on the disk surface to a second radius on the disk surface, while the write head is actively writing.

Abstract: A disk drive self-servo writes on a storage disk. Servo bursts are self-written along a track using a transducer, a position error signal (PES) indicating repeatable runout due (RRO) for the servo bursts is determined using a reference pattern, an embedded runout correction (ERC) value is calculated based on the PES and stored in a corresponding servo sector, and then the disk drive self-writes other servo bursts.

Abstract: A method and apparatus for determining embedded runout correction values uses a closed-loop system (with feedback) in a disk drive. Optionally, the embedded runout correction values may be determined after the disk drive has been manufactured and placed in the field. In addition, the embedded runout correction values may be updated after the disk drive has been manufactured and placed in the field.

Abstract: A method and apparatus for determining embedded runout correction values when self-servo writing or partial self-servo writing is disclosed. In one embodiment, a disk surface, which has servo information written thereon, is provided. The servo information is grouped into 1x servo sectors and 2x servo sectors, and the 1x servo sectors and the 2x servo sectors form a plurality of tracks. A read head servos on the 1x servo sectors associated with a track. Both position error signals due to repeatable runout for the 1x servo sectors and information related to position error signals due to repeatable runout for the 2x servo sectors are determined, while servoing on the 1x servo sectors. Embedded runout correction values for the 1x servo sectors and the 2x servo sectors are calculated.

Abstract: A method and apparatus for providing a user selectable start-up current in a disk drive are provided. A user may select a relatively high start-up current to provide a relatively fast start-up time in a disk drive. Alternatively, the user may select a relatively low maximum current draw by the hard drive to enable a relatively low power, low cost power supply to be used in connection with the hard drive, for use with applications in which a relatively long start-up time is acceptable. In connection with applications in which a low cost power supply is to be used, the maximum current drawn by the disk drive may be limited to the amount of current required by the disk drive during seek operations.