Abstract: Embodiments of the present invention provide a method of a first processor using a memory resource associated with a second processor. The method includes receiving a memory instruction from a first processor process, wherein the memory instruction refers to a shared memory address (SMA) that maps to a second processor memory. The method also includes mapping the SMA to the second processor memory, wherein the mapping produces a mapping result and providing the mapping result to the first processor.

Abstract: Provided is a method of permitting the reordering of a visibility order of operations in a computer arrangement configured for permitting a first processor and a second processor threads to access a shared memory. The method includes receiving in a program order, a first and a second operation in a first thread and permitting the reordering of the visibility order for the operations in the shared memory based on the class of each operation. The visibility order determines the visibility in the shared memory, by a second thread, of stored results from the execution of the first and second operations.

Abstract: Existing multiprocessor computing systems often have insufficient memory coherency and, consequently, are unable to efficiently utilize separate memory systems. Specifically, a CPU cannot effectively write to a block of memory and then have a GPU access that memory unless there is explicit synchronization. In addition, because the GPU is forced to statically split memory locations between itself and the CPU, existing multiprocessor computing systems are unable to efficiently utilize the separate memory systems. Embodiments described herein overcome these deficiencies by receiving a notification within the GPU that the CPU has finished processing data that is stored in coherent memory, and invalidating data in the CPU caches that the GPU has finished processing from the coherent memory. Embodiments described herein also include dynamically partitioning a GPU memory into coherent memory and local memory through use of a probe filter.

Abstract: Executing an ordering operation is disclosed. A store operation associated with storing a value into a portion of a memory is initiated. An ordering operation to ensure that the store operation, but not necessarily all store operations, are completed is executed.

Abstract: A technique for performing a plurality of operations in a shared memory system having a plurality of addresses is disclosed. The technique includes entering into a speculative mode, speculatively performing each of the plurality of operations on addresses in the shared memory system, marking addresses in the shared memory system that have been operated on speculatively as being in a speculative state, and exiting the speculative mode, wherein exiting the speculative mode includes marking the addresses in the shared memory system that have been operated on as being in a non-speculative state.

Abstract: A multi-processor, multi-cache system has filter pipes that store entries for request messages sent to a central coherency controller. The central coherency controller orders requests from filter pipes using coherency rules but does not track completion of invalidations. The central coherency controller reads snoop tags to identify sharing caches having a copy of a requested cache line. The central coherency controller sends an ordering message to the requesting filter pipe. The ordering message has an invalidate count indicating the number of sharing caches. Each sharing cache receives an invalidation message from the central coherency controller, invalidates its copy of the cache line, and sends an invalidation acknowledgement message to the requesting filter pipe. The requesting filter pipe decrements the invalidate count until all sharing caches have acknowledged invalidation.

Abstract: An apparatus for enhancing the speed of a synchronous bus includes a two register based FIFO with software control bits and a second clock signal. According to the invention, the second clock signal rd_clk is supplied by the same PLL that provides the main clock signal lg_clk. According to the invention, data is taken from the two registers in alternative clock cycles so that each of the register holds valid data for two clock cycles. A first software data bit is used to determine which of the two registers is unloaded first. Using the method and structure of the invention, the window for transferring valid data is increased and therefore the system employing the method and apparatus of the invention is more skew tolerant.

Abstract: An apparatus for enhancing the speed of a synchronous bus includes a two register based FIFO with software control bits and a second clock signal. According to the invention, the second clock signal rd_clk is supplied by the same PLL that provides the main clock signal lg_clk. According to the invention, data is taken from the two registers in alternative clock cycles so that each of the register holds valid data for two clock cycles. A first software data bit is used to determine which of the two registers is unloaded first. Using the method and structure of the invention, the window for transferring valid data is increased and therefore the system employing the method and apparatus of the invention is more skew tolerant.

Abstract: A memory controller for a memory subsystem of a computer system connects to a processor bus. The memory controller is for use with memory devices such as RDRAM or DDR SDRAM that allow for multiple open pages. Memory references are remapped by an address mapper and processed by a page tracking buffer to keep track of open pages in the memory devices. The controller also has a state machine, and an interface to memory devices. The page tracking buffer has a row address content addressable memory for determining when a reference is in an open page, and a bank content addressable memory for determining when a reference is to the same bank as an open page. The controller closes open pages of a bank prior to opening new pages in that bank. The page tracking buffer has fewer lines than the product of the maximum number of memory devices times the maximum number of simultaneously open pages of each device, but provides for tracking any page of any of the memory devices.

Abstract: A method of dynamically switching mapping schemes for cache includes a microprocessor, a first mapping scheme, a second mapping scheme and switching circuitry for switching between the first mapping scheme and the second mapping scheme. The microprocessor is in communication with the cache through the switching circuitry and stores information within the cache using one of the first mapping scheme and second mapping scheme. Also, monitoring circuitry for determining whether one of instructions and load/store operations is using the cache is included. Further, the switching circuitry switches between the first mapping scheme and the second mapping scheme based on which one of instructions and load/store operations is using the cache.

Abstract: A multiprocessor computer system has a multiplicity of sub-systems and a main memory coupled to a system controller. Some of the sub-systems are data processors, each having a respective cache memory that stores multiple blocks of data and a respective set of master cache tags (Etags), including one Etag for each data block stored by the cache memory. Each data processor includes an interface for sending memory transaction requests to the system controller and for receiving cache transaction requests from the system controller corresponding to memory transaction requests by other ones of the data processors. The system controller includes transaction activation logic for activating each said memory transaction request when it meets predefined activation criteria, and for blocking each said memory transaction request until the predefined activation criteria are met.

Abstract: A system for maintaining completion order in a multiple bus system including a bridge that posts write data includes logic units for implementing a DRAIN/EMPTY protocol. A bridge logic unit asserts an EMPTY signal when the secondary posting buffers are empty. Interrupt processing is delayed until the EMPTY signal is asserted thereby assuring that all writes are completed. If an interrupt is received and the EMPTY signal is not asserted then a DRAIN signal is asserted while the EMPTY signal is not asserted. The bridge retries all upstream write requests until EMPTY is asserted.

Abstract: An integrated processor includes an on-chip integrated input/output (IO) system (which does not have a on-chip bus) to handle direct memory access (DMA) operations from external IO units and interface with external cache and main memories. The integrated IO system includes an external cache controller that controls access to both the cache and main memory so as to maintain coherency between the cache and main memory. As part of maintaining data coherency, the cache controller prevents race conditions between instructions generated from a core logic unit within the microprocessor and DMA instructions generated from an external IO unit by giving the DMA request priority over the CPU instructions.

Abstract: A central processing unit with an external cache controller and a primary memory controller is used to speculatively initiate primary memory access in order to improve average primary memory access times. The external cache controller processes an address request during an external cache latency period and selectively generates an external cache miss signal or an external cache hit signal. If no other primary memory access demands exist at the beginning of the external cache latency period, the primary memory controller is used to speculatively initiate a primary memory access corresponding to the address request. The speculative primary memory access is completed in response to an external cache miss signal. The speculative primary memory access is aborted if an external cache hit signal is generated or a non-speculative primary memory access demand is generated during the external cache latency period.

Abstract: A computer system is disclosed including a memory subsystem and a processor subsystem having an external cache and an external mechanism for invalidating cached datablocks in the processor subsystem and for reducing false invalidation operations. The processor subsystem issues a write invalidate message to the memory subsystem that specifies a datablock and that includes an invalidate advisory indication that indicates whether the datablock is present in the external cache. The invalidate advisory indication determines whether the memory subsystem returns an invalidate message to the processor subsystem for the write invalidate operation.

Abstract: A multi-processor computer system is disclosed that reduces the occurrences of invalidate and copyback operations through a memory interconnect by disabling a first write optimization of a cache coherency protocol for data that is not likely to be written by a requesting processor. Such data include read-only code segments. The code segments, including instructions and data, are shared among the multiple processors. The requesting processor generates a Read to Share Always request upon a cache miss of a read-only datablock, and generates a Read to Share request otherwise. The Read to Share Always request results in the datablock stored in cache memory being labeled as in a "shared" state, while the Read to Share request results in the datablock being labeled as in an "exclusive" state.

Abstract: A multiprocessor computer system is provided having a multiplicity of sub-systems and a main memory coupled to a system controller. An interconnect module, interconnects the main memory and sub-systems in accordance with interconnect control signals received from the system controller. At least two of the sub-systems are data processors, each having a respective cache memory that stores multiple blocks of data and a set of master cache tags (Etags), including one cache tag for each data block stored by the cache memory. Each data processor includes a master interface for sending memory transaction requests to the system controller. The system controller processes each memory transaction and maintains a set of duplicate cache tags (Dtags) for each data processor. Finally, the system controller contains transaction execution circuitry for activating a transaction for servicing by the interconnect.

Abstract: A multiprocessor computer system is provided having a multiplicity of sub-systems and a main memory coupled to a system controller. An interconnect module, interconnects the main memory and sub-systems in accordance with interconnect control signals received from the system controller. At least two of the sub-systems are data processors, each having a respective cache memory that stores multiple blocks of data and a respective master cache index. Each master cache index has a set of master cache tags (Etags), including one cache tag for each data block stored by the cache memory. Each data processor includes a master interface for sending memory transaction requests to the system controller and for receiving cache access requests from the system controller corresponding to memory transaction requests by other ones of the data processors.

Abstract: A multiprocessor computer system has a multiplicity of sub-systems and a main memory coupled to a system controller. Some of the sub-systems are data processors, each having a respective cache memory that stores multiple blocks of data and a respective set of master cache tags (Etags), including one Etag for each data block stored by the cache memory. Each data processor includes an interface for sending memory transaction requests to the system controller and for receiving cache transaction requests from the system controller corresponding to memory transaction requests by other ones of the data processors. The system controller includes transaction activation logic for activating each said memory transaction request when it meets predefined activation criteria, and for blocking each said memory transaction request until the predefined activation criteria are met.

Abstract: A multiprocessor computer system has data processors and a main memory coupled to a system controller. Each data processor has a cache memory. Each cache memory has a cache controller with two ports for receiving access requests. A first port receives access requests from the associated data processor and a second port receives access requests from the system controller. All cache memory access requests include an address value; access requests from the system controller also include a mode flag. A comparator in the cache controller processes the address value in each access request and generates a hit/miss signal indicating whether the data block corresponding to the address value is stored in the cache memory.