Digital Equipment Corporation

Demetrios Lignos

John V Levy

Winston O Sergeant

Kent M Griggs

A secondary storage facility for a data processing system including a drive unit which connects to a pair of controllers. Switching circuits in the drive unit couple a data transfer section and a common control section for the transfer section to one or the other controller in response to selection signals. Other control sections connect to respective ones of the controllers to receive signals and a selection circuit responds by transmitting the selection signals. If one controller tries to transfer information to or from the common control section while the selection signal designates the other controller, the transfer does not occur. If the attempted transfer is to the common control section or from predetermined locations in the common control section, the attempt is retained so the drive can signal back through the other controller when the selection signal can change. If the attempted transfer is from the common control section, then the drive transmits back to the controller a unique code.

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Chelmsford, MA, United States of America

Demetrios Lignos