Digital Equipment Corporation

Robert E Willard

Richard Franklin Lary

David William Thiel

Barry L Rubinson

Catharine Van Ingen

Verell Boaen

William Watson

R Stephen Polzin

Edward A Gardner

James N Leahy

A dual addressing arrangement comprises a complex address pointer within entries of a communication queue used by a port driver and an port adapter when exchanging information in a host computer. The complex address pointer comprises a virtual address portion and a physical address portion. The port driver uses the virtual address portion to ascertain the location of entry structures, while the port adapter uses the physical address portion to locate the structures in a host memory. The arrangement and interpretation of the address portions of the complex pointers within an entry depend upon the direction of information flow, i.e., the passing of messages from the port driver to the port adapter using a driver-to adapter queue or the passing of responses from the adapter to the driver using an adapter-to-driver queue.

Dual addressing arrangement for a communications interface architecture

A method and apparatus for optimizing the performance of a multibus data processing system is provided. An I/O controller is coupled to the I/O bus and includes MORE bit setting means for initiating a MORE stream transaction on the I/O bus and for thereafter terminating the MORE stream transaction. An adapter coupling the I/O bus to the system bus, is configured to receive the MORE stream transaction and transfer it to main memory. The adapter includes MORE bit decoding means for identifying the beginning and the end of the MORE stream transaction, and for identifying whether the MORE stream transaction is a READ or WRITE transaction. The adapter also includes a first buffer for receiving data from the I/O bus and transferring the data to the memory in accordance with the memory's full block transfer size, and a second buffer for receiving a full block of data and transferring that data in accordance with the I/O bus transaction limitations. The adapter is capable of invalidating data located in the first buffer and clearing data located in the second buffer in accordance with a discard transaction when the I/O controller fails to properly terminate the MORE stream transaction.

Method and apparatus for transferring data processing data transfer sizes

A communication interface between a port driver and an port adapter of a host computer includes a singly-linked queue resident in a host memory of the computer. The queue includes a header element and a stopper element with message entries linked therebetween. The message entries contain information to be exchanged between the port driver and port adapter. Each message entry includes at least a carrier that contains a forward link pointer to the next entry in the queue and message/response specific control information. The stopper element identifies the end of the queue and is distinguishable from a message entry by a valid indicator, e.g., the state of at least one bit of the forward link pointer. Functionally, the stopper entry allows the port driver and port adapter to concurrently insert and remove message entries of the singly-linked queue in a reliable manner without the use of any external synchronization mechanism.

Queue apparatus and mechanics for a communications interface architecture

A memory mapping system for use by a port adapter in a computer facilitates access to named data buffers in host memory. The system generally comprises a mechanism that enables the adapter to efficiently translate the data buffer name to physical address locations in host memory without knowledge of the memory management policies of the computer. Specifically, the system includes various data structures and pointers that allow the port adapter to view host memory in 'port pages' when accessing memory locations of a named data buffer. The data locations are virtually, but not physically, contiguous and the invention provides efficient identification of the physical addresses of the locations.

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Andover, MA, United States of America

Robert E Willard