Abstract: A system and method for guaranteeing transactional fairness among multiple requesters contending for a common resource in a cache-coherent multiprocessor system is described. Batch processing is used to control servicing of multiple requests made by multiple requesters (such as processors) of a common resource in a cache-coherent multiprocessor system. Specifically, identification numbers are assigned to requests as they are received from the multiple requesters. The identification numbers are then used in conjunction with batch processing to prioritize and guarantee servicing of the requests.

Abstract: A system and method for managing memory data is provided. Data stored within a main memory may be requested by multiple requesters that may include one or more cache memories. When the data is provided by the main memory to a requester, it will be provided in a state that is based on the way the data was recently used by the requesters. For example, if a pattern of read-only usage has been established for the data, the data will be returned to a requester in a shared state. If data that was provided in a shared state must be updated such that the requester is required return to main memory to obtain read/write privileges, the main memory will thereafter provide the data in an exclusive state that allows write operations to be completed. This will continue until a pattern of read-only usage is again established.

Abstract: A data by-pass system for a hierarchical, multi-level, memory is disclosed. The by-pass system provides by-pass interfaces between storage devices located at predetermined levels within the memory hierarchy. The hierarchical memory system of the preferred embodiment includes a main memory coupled to multiple first storage devices that each stores addressable portions of data signals retrieved from the main memory. To facilitate a more efficient transfer of data between the various storage devices in the memory system, at least one by-pass interface coupling associated ones of the first storage devices is provided. Data retrieved from a target one of the first storage devices in response to a main memory request can be routed to a different requesting one of the first storage devices via the by-pass system without requiring the use of the main memory data interfaces.

Abstract: A hierarchical memory structure includes a directory-based main memory coupled to multiple first storage devices, each to store data signals retrieved from the main memory. Ones of the first storage devices are further respectively coupled to second storage devices, each to store data signals retrieved from the respectively coupled first storage devices. Fetch requests to retrieve data signals are issued by ones of the storage devices to the main memory. In response, the main memory determines where the most recent data copy resides, and issues a return request, if necessary to retrieve that copy for the requesting storage device. A speculative return generation logic circuit is coupled to at least two of the first storage devices to intercept the fetch requests. In response to an intercepted request, the speculative return generation logic circuit generates a speculative return request directly to one or more of the other coupled first storage devices.

Abstract: A system and method are provided to avoid deadlocks when performing non-atomic operations on data in a shared memory accessed by multiple processors, whereby the shared memory sends messages to implement a split lock. Via the messages, the requesting processor is granted exclusive access to the shared memory so that no other processor may access the same data until after the non-atomic operation has completed. The messages used to avoid the deadlock include a split lock request, a lock message, a grant message, a gone idle message and a release idle message. By using the above messages, the system accepts requests from multiple processors for exclusive access to memory, orders all of the requests, and awards exclusive access to the first processor to make a request. The system can include a cache memory, associated with a requesting processor, which sends a lock request to the main memory in response to a split lock request from a requesting processor.

Abstract: A system and method for avoiding deadlocks when performing non-atomic operations on data in a shared memory accessed by multiple processors that sends messages to implement a split lock. Via the messages, the requesting processor is granted exclusive access to the shared memory so that no other processor may access the same data until after the non-atomic operation has completed. The messages used to avoid the deadlock include a split lock request, a lock message, a grant message, a gone idle message and a release idle message. By using the above messages, the system and method of the present invention accepts requests from multiple processors for exclusive access to memory, orders all of the requests, and awards exclusive access to the first processor to make a request. The system can include a cache memory, associated with a requesting processor, which sends a lock request to the main memory in response to a split lock request from a requesting processor.

Abstract: A system and method for optimizing the amount of time it takes for a requestor (device) to receive data from a memory storage unit in a multi-requestor bus environment. The present invention provides a unidirectional response signal, referred to as an early warning signal, sent from a memory storage unit to a device, sometime after that device has executed a fetch request for data, to alert the device that the data is forthcoming. This early warning signal allows the device to arbitrate for the data bus so that when the data arrives, the device will have exclusive ownership of the data bus to accept the data immediately. The present invention comprises a main memory, a cache memory, one or more processor modules, one or more I/O modules, and an early warning bus. The cache memory is connected to the main memory via an interface bus. The processor modules are connected to the cache memory via a processor interface bus. The I/O modules are connected to the main memory via an I/O interface bus.

Abstract: A low latency software and hardware interface between a microprocessor and Network Interface Unit is disclosed. The Network Interface Unit interfaces to the microprocessor's Level 2 cache interface, which provides burst transfers of cache lines between the microprocessor and Network Interface Unit. The Network Interface Unit is memory mapped into the microprocessor's address space. Two memory mapped cache lines are used to write commands to the Network Interface Unit's Write Window and another two cache lines are used to read results of the commands from the Network Interface Unit's Read Window. The Write Window is a three port register file. Data is written into one write port and read simultaneously from two read ports. One read port is used during read operations to the Write Window while the other is used during command execution to move data to the Internal Structures block. The Read Window is a 2-1 multiplexor that is 128 bits wide.

Abstract: Method and apparatus for verifying the result of an arithmetic operation. The invention provides a time and cost efficient method of performing error detection on the result of an arithmetic operation; especially for a division operation. It does so through the novel use of a Carry-Save Adder (CSA). A CSA is known in the art to be faster and less costly to implement than the use of a full adder.

Abstract: A computer system executes steps to provide results in an order different from an intended order. Instructions are concatenated into a plurality of jobs. Different invocations of a variable within the computer instruction stream may be assigned respectively different storage locations and each storage location may correspond to a different job. When all the storage locations associated with a particular job indicate available resources (e.g. valid variable input), the job may be executed. A mechanism allows for job re-execution, if needed, due to interrupt or error.

Abstract: An array of various types of processors for the purpose of simulating computer functions for large computer systems. These functions may vary from simple AND, OR and other functions to large arithmetic logic units and even random access memories. The simulation array is a tree-type array where the leaves of the tree are the actual logic simulation processors with the other processors serving as nodes which route change of value notices among the various logic simulation processors.

Abstract: A mechanism for a data processor that is adapted to receive strings of object code, form them into higher level tasks and to determine sequences of such tasks which are logically independent so that they may be separately and concurrently executed by a plurality of processing elements. The mechanism makes all memory accesses required by the various tasks and stores those tasks along with corresponding pointers or references to local memory in which the various data items have now been stored. The mechanism employs a symbol translation table in which the tasks are stored in forms of queues along with symbols representing the various references or pointers to local memory. In this manner, various data items can be assigned different symbols or symbolic names for use with different tasks thus further limiting dependency between various tasks and controlling data changes.

Abstract: A data processor having a plurality of processing elements and a mechanism to receive strings of object code, form them into higher level tasks and to determine sequences of such tasks which are logically independent so that they may be separately and concurrently executed by the plurality of processing elements. The mechanism makes all memory accesses required by the various tasks and stores those tasks along with corresponding pointers or references to local memory in which the various data items have now been stored. The mechanism employs a symbol translation table in which the tasks are stored in forms of queues along with symbols representing the various references or pointers to local memory. In this manner, various data items can be assigned different symbols or symbolic names for use with different tasks thus further limiting dependency between various tasks and controlling data changes.

Abstract: A mechanism for a data processor that is adapted to receive strings of object code, form them into higher level tasks and to determine sequences of such tasks which are logically independent so that they may be separately executed. The mechanism makes all memory accesses required by the various tasks and stores those tasks along with corresponding pointers or references to local memory in which the various data items have now been stored. The mechanism employs a symbol translation table in which the tasks are stored in forms of queues along with symbols representing the various references or pointers to local memory. In this manner, various data items can be assigned different symbols or symbolic names for use with different tasks thus further limiting dependency between various tasks and controlling data changes.