Unisys Corporation

Jeffrey E Dremann

Todd M Rimmer

Duane J McCrory

William P Jordan

Apparatus for implementing input/output (I/O) operations in a computer system operating under the control of a UNIX* operating system includes a dedicated communications processor in addition to the main or host processor. These two processors communicate via a shared memory which may be independently accessed by each processor. The functions performed by the terminal I/O driver and the line discipline modules are divided between the host and communications processors. The communications processor performs all canonical processing of the data received from the terminal I/O devices. It also maintains a data structure that indicates the instantaneous status of each terminal I/O device. Using this data structure, the communications processor is able to operate in a substantially interrupt-free environment, polling only those I/O devices that are indicated, in the status data structure, as needing service. A message facility in the shared memory controls communication between the processors. Each processor sends messages to the other through a dedicated circular queue. To receive a message, a processor examines the sending queue of the other processor. Response messages are sent back to the sending processor using the same message buffer as was used for the original message.

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Coatesville, PA, United States of America

Jeffrey E Dremann