Digital Equipment Corporation

Quantum Corporation

James C Stegeman

Donald W Smelser

Lawrence A Chisvin

Peter B Bareham

Martin C Blitz

Disclosed is a solid state disk drive, including a volatile, electronic RAM, memory and a non volatile, magnetic disk. The drive continuously saves unique data stored in the memory back to the disk. Additionally, the drive includes a number of tables and bit fields, in both volatile electronic memory and disk, for generally keeping track of what data has been restored from disk to memory, what data in the memory has been modified since it was restored from disk, and what modified data in the memory has been saved back to disk. In the event of a primary power outage, the drive first saves the volatile tables onto disk, and then saves the volatile, modified data onto disk, while using auxiliary power. If, however, auxiliary power is lost before any or all of the modified data is saved on disk, the saved tables provide information which enables the drive to distinguish the valid from the invalid data on disk.

Solid state disk drive unit having on-board backup non-volatile memory

A method and apparatus for error detection is disclosed. A data word and its check bits are read from memory, and new check bits are generated form the data word read. A logical operation is performed between the new check bits and the check bits read from memory to generate a syndrome. The syndrome is decoded to detect the presence or absence of an uncorrectable error. If an uncorrectable error is detected, a logical operation is performed between the new check bits and a byte write error code to generate a third set of check bits, which are then written into memory along with the data word.

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Acton, MA, United States of America

James C Stegeman