Seagate Technology Incorporated

Sperry Corporation

Don M Robinson

Henry Elwood Davenport

Prafulla Bollampalli Reddy

Robert E Swenson

David M Lewis

Lawrence D Sasscer

Kathleen Anne Duncan

Marvin Mang-Yin Lum

Dhlrubwai N Desai

A disc controller services a host 'read' command, without intervention by the disc controller's microcontroller, if the requested data is found in the disc controller's cache. The disc controller stores at least one cache entry. Each cache entry includes an address, a logical Bit, a valid Bit and a set of four buffer parameters: upper limit address, base address, pointer to the sector count and sector count. Each host command is decoded by the disc controller, and if the command is a 'read' command the address in the cache entry is compared against the address in the host command. If the addresses match and the cache entry address is marked as being valid by its Valid bit, a 'cache hit' signal is generated and the disc controller starts transferring the data requested by the host without waiting for the disc controller's microprocessor to process the host command. In particular, a sequencer and data transfer circuitry automatically generate a host interrupt request signal and transfer to the host at least a subset of the requested set of data blocks specified by each read command when a cache hit signal is generated. The disc controller includes circuitry for updating the information stored in the cache entry so that said updated information stored in the cache entry identifies data blocks in the cache sequentially subsequent to those data blocks transferred to the host.

Disc drive controller with apparatus and method for automatic transfer

Connected blocks of micro-instructions are reloaded to a register file in a sequencer, which is used for controlling an interfacing between a host computer, a magnetic disk-drive, and a buffer memory. This provides for efficiently reloading sequencer microinstructions into a relatively small sequencer-memory space and minimizes use of external system resources for reloading microinstructions. This avoids the sequencer having to remain in a wait condition until a system processor completes higher priority tasks and becomes available for reloading instructions to memory cells of the sequencer. The method includes storing a plurality of blocks of microinstructions in a buffer memory device. A first block of microinstructions is stored in a register file. A second block of microinstructions stored within the buffer memory device is called using microinstructions contained within the first block of microinstructions. The second block of microinstructions are loaded into the register file, where the second block of microinstruction contain microinstructions for loading a third block of microinstructions into the register file, and so on. The sequencer interfaces with a buffer memory, which stores a plurality of blocks of microinstructions. A register file stores a first block of microinstructions, where the first block of microinstructions includes microinstructions for selecting a second block of microinstructions from the buffer memory. The first block of microinstruction includes microinstructions for subsequently loading the selected second block of microinstructions into the register file.

Method and apparatus for reloading microinstruction code to a SCSI

The defect list, as supplied by the manufacturer, is stored on the outer tracks of the disk. It is merged with the user supplied media defect list during formatting and used to flag defective sectors. During initialization the merged defect list is loaded into a section of dynamic memory so that it is accessible during seeking of a particular address.

Method for mapping around defective sectors in a disc drive

The defect list, as supplied by the manufacturer, is stored on the outer tracks of the disc. It is merged with the user-supplied media defect list during formatting and used to flag defective sectors. During initialization the merged defect list is loaded into a section of dynamic memory so that it is accessible during seeking of a particular address.

In a system having a host processor connected through a storage control unit to a cache store and a plurality of disk devices, segments of data which have been written to, while resident in the cache store, are transferred to the disks at some later time. If an abnormal condition, such as a bad spot on the disk, prevents the transfer of a segment from the cache store to the disk, an indicator is set for that segment by the storage control unit to prevent further attempts to transfer the segment. A segment whose indicator is set remains in the cache store until the host processor issues an initialize or a reset segment command.

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Santa Clara County, CA, United States of America

Don M Robinson