Abstract: A method and apparatus for ensuring fair and efficient use of a shared memory buffer. A preferred embodiment comprises a shared memory buffer in a multi-processor computer system. Memory requests from a local processor are delivered to a local memory controller by a cache control unit and memory requests from other processors are delivered to the memory controller by an interprocessor router. The memory controller allocates the memory requests in a shared buffer using a credit-based allocation scheme. The cache control unit and the interprocessor router are each assigned a number of credits. Each must pay a credit to the memory controller when a request is allocated to the shared buffer. If the number of filled spaces in the shared buffer is below a threshold, the buffer immediately returns the credits to the source from which the credit and memory request arrived.

Abstract: A system and method is disclosed to maintain the coherence of shared data in cache and memory contained in the nodes of a multiprocessing computer system. The distributed multiprocessing computer system contains a number of processors each connected to main memory. A processor in the distributed multiprocessing computer system is identified as a Home processor for a memory block if it includes the original memory block and a coherence directory for the memory block in its main memory. An Owner processor is another processor in the multiprocessing computer system that includes a copy of the Home processor memory block in a cache connected to its main memory. Whenever an Owner processor is present for a memory block, it is the only processor in the distributed multiprocessing computer system to contain a copy of the Home processor memory block.

Abstract: A method and architecture for improving the usability and manufacturing yield of a microprocessor having a large on-chip n-way set associative cache. The architecture provides a method for working around defects in the portion of the die allocated to the data array of the cache. In particular, by adding a plurality of muxes to a way or ways in the data array of an associative cache having the shorter paths to the access control logic, each way in a bank can be selectively replaced or remapped to the ways with the shorter paths without adding any latency to the system. This selective remapping of separate ways in individual banks of the set associative cache provides a more efficient way to absorb defects and allows more defects to be absorbed in the data array of a set associative cache.

Abstract: A computer system has a set-associative, multi-way cache system, in which at least one way is designated as a fast lane, and remaining way(s) are designated slow lanes. Any data that needs to be loaded into cache, but is not likely to be needed again in the future, preferably is loaded into the fast lane. Data loaded into the fast lane is earmarked for immediate replacement. Data loaded into the slow lanes preferably is data that may not needed again in the near future. Slow data is kept in cache to permit it to be reused if necessary. The high-performance mechanism of data access in a modem microprocessor is with a prefetch; data is moved, with a special prefetch instruction, into cache prior to its intended use. The prefetch instruction requires less machine resources, than carrying out the same intent with an ordinary load instruction. So, the slow-lane, fast-lane decision is accomplished by having a multiplicity of prefetch instructions.

Abstract: A method and architecture for improving the usability and manufacturing yield of a microprocessor having a large on-chip n-way set associative cache. The architecture provides a method for working around defects in the portion of the die allocated to the data array of the cache. In particular, by adding a plurality of muxes to a way or ways in the data array of an associative cache having the shorter paths to the access control logic, each way in a bank can be selectively replaced or remapped to the ways with the shorter paths without adding any latency to the system. This selective remapping of separate ways in individual banks of the set associative cache provides a more efficient way to absorb defects and allows more defects to be absorbed in the data array of a set associative cache.

Abstract: A computer system has a plurality of processors wherein each processor preferably has its own cache memory. Each processor or group of processors may have a memory controller that interfaces to a main memory. Each main memory includes a “directory” that maintains the directory coherence state of each block of that memory. One or more of the processors are members of a “local” group of processors. Processors outside a local group are referred to as “remote” processors with respect to that local group. Whenever a remote processor performs a memory reference for a particular block of memory, the processor that maintains the directory for that block normally updates the directory to reflect that the remote processor now has exclusive ownership of the block. However, memory references between processors within a local group do not result in directory writes.

Abstract: A system and method is disclosed to maintain the coherence of shared data in cache and memory contained in the nodes of a multiprocessing computer system. The distributed multiprocessing computer system contains a number of processors each connected to main memory. A processor in the distributed multiprocessing computer system is identified as a Home processor for a memory block if it includes the original memory block and a coherence directory for the memory block in its main memory. An Owner processor is another processor in the multiprocessing computer system that includes a copy of the Home processor memory block in a cache connected to its main memory. Whenever an Owner processor is present for a memory block, it is the only processor in the distributed multiprocessing computer system to contain a copy of the Home processor memory block.

Abstract: A system and method is disclosed to maintain the coherence of shared data in cache and memory contained in the nodes of a multiprocessing computer system. The distributed multiprocessing computer system contains a number of processors each connected to main memory. A processor in the distributed multiprocessing computer system is identified as a Home processor for a memory block if it includes the original memory block and a coherence directory for the memory block in its main memory. An Owner processor is another processor in the multiprocessing computer system that includes a copy of the Home processor memory block in a cache connected to its main memory. Whenever an Owner processor is present for a memory block, it is the only processor in the distributed multiprocessing computer system to contain a copy of the Home processor memory block.

Abstract: A technique for verification of a complex integrated circuit design, such as a microprocessor, using a randomly generated test program to simulate internal events and to determine the timing of external events. The simulation proceeds in two passes. During a first pass, the randomly generated test program and data vectors are applied to a simulation model of the design being verified. During this first pass, an internal agent collects profile data about internal events such as addresses and program counter contents as they occur. During a second pass of the process, the profile data is used to generate directed external events based upon the data observed during the first pass. In this manner, the advantages of rapid test vector generation provided through random schemes is achieved at the same time that a more directed external event correlation is accomplished.