International Business Machines Corporation

Motorola Corporation

Michael Scott Allen

Ravi Kumar Arimilli

John Michael Kaiser

William Kurt Lewchuk

Robert J Reese

Charles Roberts Moore

Michael Julio Garcia

Robert Alan Cargnoni

Jose Melanio Nunez

Yoanna Baumgartner

David W Todd

Brad B Beavers

Jen-Tian Yen

The present invention provides a system and method for efficient execution of load reserve (LARX) and store conditional (STCX) instructions in a superscalar processor. A system for efficiently providing a LARX instruction in a superscalar processor is disclosed. The system comprises a data cache (Dcache) for receiving the LARX instruction. The data cache further includes a decoder means for setting and resetting of a validation of the load reserve instruction, an internal cache for receiving address information and for providing data. The system also includes a register means for receiving the LARX instruction and a controller means for providing a physical address based upon the address information. The system provides for the validation being accomplished in one cycle for the LARX instruction when there is a hit on the internal data cache.

High performance implementation of the load reserve instruction in a

A method and system for the enhanced efficiency of data transfers from memory to multiple processors in a data processing system. Each of the multiple processors has an associated buffer for storing data transferred via a common bus which couples the processors and memory together. Each of the multiple processors continually monitors the common bus and is capable of asserting a selected control signal in response to an attempted activity of another one of the multiple processors which would violate data coherency within the data processing system during a particular period of time following the attempted activity. Data is transferred from memory to a buffer associated with one of the multiple processors and stored in the buffer in response to a request from the processor associated with the buffer prior to expiration of the particular period of time and prior to a determination of whether or not this transfer will result in a possible data coherency problem. The common bus is continually monitored during the particular period of time. Transfer of the data from the buffer to the processor is prohibited in response to a presence on the common bus of the selected control signal prior to expiration of the particular of time. Transfer of the data from the buffer to the processor is permitted in response to an absence on the common bus of the selected control signal.

Method and system for enhanced efficiency of data transfers from memory

A system and method are provided that use a determination of bad data parity and the state of an error signal (Derr.sub.--) as a functional signal indicating a specific type of error in a particular system component. If the Derr.sub.-- signal is active, the parity error recognized by the CPU was caused by a correctable condition in a data providing device. In this instance, the processor will read the corrected data from a buffer without reissuing a fetch request. When the CPU finds a parity error, but Derr.sub.-- is not active a more serious fault condition is identified (bus error or uncorrectable multibit error) requiring a machine level interrupt, or the like. And, when no parity is found by the CPU and Derr.sub.-- is not active, then the data is known to be valid and the parity/ECC latency is eliminated, thereby saving processing cycle time.

Low latency error reporting for high performance bus

A method and system are provided for communicating between devices. A signal is output from a first device. In response to the signal, at least one action is initiated by a second device. An indication is output of whether the second device completed the action and of whether operation of the second device is independent of the first device reoutputting the signal.

System and method for communicating between devices

A method and system in a data processing system for transferring data from a first device to a second device within the data processing system. The data processing system includes a data bus, an address bus, a first address space associated with a memory and a second address space associated with an input/output device. Initially, an operation request package is transmitted to a second device from a first device, which informs the second device of the total amount of data to be transferred. A transfer signal is then transmitted in the data processing system. The transfer signal identifies the transfer as a transfer concerning an address in the second address space associated with the input/output device. A first address package is then transmitted to the second device from the first device on the address bus. The first address package includes a transfer identifier, a first identifier associated with the first device and a second identifier associated with the second device. A second address package, comprising a byte count and an address, are transmitted to the second device from the first device on the address bus. If data is to be transferred, the data is then transferred on the data bus. Finally, a reply signal may be transmitted between the first and second devices, acknowledging the success or failure of the data transfer.

System for transferring data between input/output devices having

An efficient multiprocessor address transfer mechanism is utilized within a data processing system including a plurality of bus devices. The present invention places control of the flow of address bus operations within the system controller rather than the bus devices, e.g., a master processor. The system controller issues an address bus grant, in response to an address bus request from a particular bus device, and shortly after that issues another signal notifying the granted bus device that it must now disable the address bus. Furthermore, upon receipt of the signal indicating disablement of the address bus, other bus devices may then snoop, or sample, the address bus.

System and method for allocating bus resources in a data processing

A system and method which utilizes a unique bus protocol in conjunctions plural Dval.sub.-- control signals to minimize the dead time between blocks of data being transferred between components is a data processing system. The present invention introduces another latch-to-latch data valid control signal and alternates the usage of this signal during back to back data transfers from the same or different bus devices. In this manner the restore and tristate dead cycles are totally overlapped with the data transfer and the minimum possible number of dead cycle(s) is achieved between different blocks of data transfers. With the method of the present invention, data providers alternately activate the Dval.sub.-- signals and data receivers look at all Dval.sub.-- signals and if any one of them is active, then the data is considered valid and can be read.

Alternating data valid control signals for high performance data transfer

A multiprocessor system utilizing a plurality of bus devices coupled via a shared bus utilizes a specially coded signal to notify a bus device initiating a read or a read with intent to modify operation that the requested data, or cache line, is in a modified state within a cache of another bus device. Unlike the modified response signal, this special signal is sent along with the requested data from the one bus device to the requesting bus device, indicating that this data has priority over any data being sent from the memory system coupled to the shared bus. The present invention allows for cache-to-cache and cache-to-memory-and-cache operations.

Cache coherency in a multiprocessing system

An arbitration protocol (68) comprises the steps of receiving a first (70) and a second (74) plurality of resource request signals, and either, granting the shared resource to a selected one of a first plurality of resource users (72) or granting the shared resource to a selected one of a second plurality of resource users (76). A differing one of each of a first plurality of resource users and of each of a second plurality of resource users generates a differing one of the first plurality of resource request signals and a differing one of the second plurality of resource request signals, respectively. Each one of the first and the second plurality of resource request signals corresponds to a first logic state if a particular one of the first or second plurality of resource users requests use of a shared resource. The shared resource is granted to a selected one of the first plurality of resource users according to a first arbitration protocol if at least one of the first plurality of resource request signals corresponds to the first logic state. The shared resource is granted to a selected one of the second plurality of resource users according to a second arbitration protocol if none of the first plurality of resource request signals corresponds to the first logic state and at least one of the second plurality of resource request signals corresponds to the first logic state.

Priority arbitration protocol with two resource requester classes and

A multiprocessing system utilizes a bus protocol having two response windows. The first response window is at a fixed latency from the transmission of a bus request and/or address, while the second response window, utilized for coherency reporting, is placed a configurable number of clock cycles after the bus request and address to allow for longer access, or snoop, times to perform a cache directory look-up within other bus devices. The first response window reports error or flow control and error status. Furthermore, a method had been described, which implements the reporting of response information in a flexible and high performance manner.

Dual latency status and coherency reporting for a multiprocessing system

A method and system in a data processing system for transferring data from a first device to a second device within the data processing system. The data processing system includes a data bus, an address bus, a first address space associated with a memory and a second address space associated with an input/output device. Initially, a transfer signal is transmitted in the data processing system. The transfer signal identifies the transfer as a transfer concerning an address in the second address space associated with the input/output device. A first address package is then transmitted to the second device from the first device on the address bus. The first address package includes a transfer identifier, a first identifier associated with the first device and a second identifier associated with the second device. A second address package, comprising a byte count and an address, are transmitted to the second device from the first device on the address bus. If data is to be transferred, the data is then transferred on the data bus. Finally, a reply signal may be transmitted between the first and second devices, acknowledging the success or failure of the data transfer.

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Austin, TX, United States of America

Michael Scott Allen