Hewlett-packard Company

Digital Equipment Corporation

Barry J Flahive

Richard G Bahr

Bernard L Stumpf

Dale Calvin Morris

Robert E Stewart

Stephen G Burger

Stephen J Ciavaglia

James B Keller

Michael L Ziegler

William R Bryg

Jerome C Huck

Ruby B Lee

William F Bruckert

Hugh C Lauer

Jeffrey D Kurtze

John S Yates, Jr

Peter J Rado

Andrew Milia

Michael Kahaiyan

John Manton

David Potter

George M Stabler

Jeff Kurtze

John J Grady, Iii

James V Lacy

Ruby B L Lee

A computer apparatus incorporating special instructions to force load and store operations to execute in program order. The present invention provides a new and novel store instruction that is suspended until all prior store instructions have been completed by an associated CPU. Also, a new load instruction is provided which blocks any subsequent load instructions from executing until this load instruction has been completed by an associated CPU. These instructions allow for high efficiency computer systems to be implemented which optimize instruction throughput by executing subsequent instructions while waiting for a prior instruction to complete.

Computer apparatus having special instructions to force ordered load and store operations

A computer apparatus which detects a store or load operation into or from a shared memory page by a program that does not provide for synchronization when executed by a CPU that completes instructions out of program order. After the store or load is detected, the CPU explicitly orders operations into the shared memory page. Store operations are ordered such that no new store into the shared memory page is performed until all prior store operations into the shared memory page are complete. Also, load operations are ordered such that load operations from the shared memory page are performed in program order. This ordering is achieved by maintaining a process bit and a memory attribute bit associated with a shared memory page. When both bits are true, all load or store operations referencing the shared memory page are ordered.

Computer that selectively forces ordered execution of store and load

A computer system having a plurality of processors sharing common memory and data bus structures and operable to perform atomic operations which comprise several instruction actions, wherein the processor performing the atomic operation prevents memory access interruptions by other processors by locking out other processors during the atomic operation. The system bus includes signal paths accommodating bus lock request and bus lock signals which are provided and received by each processor, which signals are initiated by specific bus lock and lock release instructions added to each processor instruction set.

Method and apparatus for bus lock during atomic computer operations

A method and apparatus for granting, to a select processor in a multiprocessor computing system, exclusive access to a bus for issuance of address, data and command signals thereover, wherein each processor includes bus lock request and bus lock assert elements which provide corresponding bus request and bus hold signals which are recognized by corresponding elements included in other processors connected to the bus. The bus lock according to the present invention assures the processor having lock status of privacy on the bus necessary to complete a specified operation without interruption from the other processors.

Multiprocessor bus locking system with a winning processor broadcasting

Apparatus and method for concurrent dispatch of instruction words which selectively comprise instruction components which are separately and substantially simultaneously received by distinct floating point and integer functional units. The instruction words are powers of 2 in length, (measured in terms of the smallest machine addressable unit) typically a 4 byte longword and an 8 byte quadword aligned to the natural boundaries also corresponding to powers of 2. To provide maximum operating efficiency, each functional (or processing) unit executes a component of an instruction word during an execution cycle. The type and length of the instruction word are indicated by one of the bit fields of the instruction word, which permits the apparatus to properly detect, store and transfer the instruction word to the appropriate functional unit. The invention combines the encoding efficiency of variable length instruction combined combined with the enhanced processing speed of simultaneous operation of all available functional units, to provide the execution efficiency of systems with a single instruction length.

Data processing system for concurrent dispatch of instructions to

A data transfer system for use in transferring data between a memory and an input/output system in a digital data processing system. The data transfer system includes a plurality of buffers into which data can be loaded from the memory or the input/output system. A buffer control selects the buffer to be loaded, and control signals from the memory govern the transfer of data from the memory into and out of the selected buffer.

Buffer system for input/output portion of digital data processing system

A cache memory unit is disclosed in which, in response to the application of a write command, the write operation is performed in two system clock cycles. During the first clock cycle, the data signal group is stored in a temporary storage unit while a determination is made if the address signal group associated with the data signal group is present in the cache memory unit. When the address signal group is present, the data signal group is stored in the cache memory unit during the next application of a write command to the cache memory unit. If a read command is applied to the cache memory unit involving the data signal group stored in the temporary storage unit, then this data signal group is transferred to the central processing unit in response to the read command. Instead of performing the storage into the cache memory unit as a result of the next write command, the storage of the data signal in the cache memory unit can occur during any free cycle.

Apparatus and method for providing a cache memory unit with a write

An arbitration network for use in a data multiprocessing system that includes a functional unit, such as a memory module, that is shared by several requestor devices, such as data processors, wherein access is granted to the shared functional unit through a common data bus on a rotating priority basis and wherein the arbitration cycle of the functional unit for determining priorities of the requestor devices is performed near the end of each operational cycle of the functional unit so that the next requestor device initiates its operational cycle immediately succeeding a current operational cycle then transacting thereby to minimize idle bus periods which would otherwise occur during arbitration cycle sequencing. When the bus is idle and only one request for access is made, the arbitration network foregoes the complete arbitration cycle and issues the grant to the requesting device thereby providing an earlier initiation of the data transfer cycle of the functional unit.

Arbitration scheme for a multiported shared functional device for use in

A digital data processing system including an interconnection for the various elements that constitute the system. Each element that connects to the interconnection is called a nexus, and each nexus in the system can communicate with other nexuses. A central clocking circuit generates timing signals that control such communications on a synchronous basis. The clocking circuit includes oscillator, control and sequencing circuits that produce phase and clocking signals that are coupled to each nexus. Each nexus contains receivers and decoders for converting the phase and clocking signals into a sequence of internal timing signals that synchronizes the operation of the nexus to transfers among the nexuses.

System timing means for data processing system

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Westford, MA, United States of America

Barry J Flahive