Abstract: A direct access storage device (DASD) performs defect mapping and translates logical block address references to physical block addresses with a virtual track (VT) table and a virtual sector (VS) table, and also uses a prototype table (VSpr) that contains index locations for all virtual tracks that contain spares and identifies sectors located on the track, and a reassign table (VSre) that contains exceptions from the prototype table due to reassignment of a spare sector. The VS table contains index locations that identify a group of sectors located on the track corresponding to the index location, but does not include spares. The VT table includes columns that point into the VSpr and VSre tables. The overall size of the defect mapping tables is reduced by removing the spare sectors from the VS table, thereby more efficiently utilizing storage system resources.

Abstract: Method and system aspects for controlling spindle motor speed during head loading in a disk drive are described. The aspects include inputting a time-varying reference velocity profile signal, and selecting a controller to control spindle motor speed. Further included is feeding forward control signals sufficient to precompensate for drag during a head loading event and maintain spindle motor speed within an operating tolerance.

Abstract: A direct access storage device (DASD) servo control system includes a servo controller that makes an estimate of disk actuator arm position and velocity as for a regular, expected PES signal sample time, and then alters the estimate for an odd sample time using a simplified estimation function. The altered estimate is generated after determining the amount of time by which the odd sample time is longer than the regular sample time. An odd sample time event is recognized and the odd sample time is forced longer than the regular sample time by skipping a disk control signal computation interval. In this way, the estimated position and velocity of the disk arm is improved for odd sample times, even where the change in one PES sample time may be unrelated to the change in any subsequent PES sample times.

Abstract: A data storage disk drive system uses a no-ID disk architecture. The disk is formatted by mapping the disk in the desired format and allocating the defective regions to defective sectors. The list of defective sectors is then stored in a table. The user may selectively perform this format operation without the need to perform an AC erase of the entire disk and/or a write of all data sectors on the disk.

Abstract: A no-ID zone-bit-recording data recording disk drive system having an interface processor and a servo processor is described wherein track seek time is substantially reduced by the following two step seek process. The interface processor converts a logical block address (LBA) to an estimated physical block address (EPBA) using a defect map where the EPBA is communicated to the servo processor. The servo processor uses a zone table and converts the EPBA to an estimated zone-cylinder-head-sector (ZCHS) value which is used to initiate actuator arm movement and moving the appropriate head over the disk in the direction of sought after track. Concurrently with the servo processor computation and actuator arm motion, the interface processor generates an exact PBA and communicates the exact PBA to the servo processor. The servo processor converts the exact PBA to exact ZCHS values and modifies the actuator arm motion so the head can be exactly positioned over the sought after track.

Abstract: A disk drive or comparable device is described which has two microprocessors connected by a communication link. One of the microprocessor accesses nonvolatile storage means containing object code in a compressed format for the other microprocessor. When the device is reset the microprocessor having access to the ROM decompresses the object code and transmits it to the second microprocessor. The compression scheme stores indexes into a table for the N most frequent words in the object code and leaves any excess words uncompressed. The uncompressed words are distinguished from the indexes by a set of flags which may be stored in-line with the compressed code or stored separately to avoid having to perform bit shifting to restore elements to byte boundaries.