Abstract: A method for insuring data consistency between a plurality of individual processor cache memories and the main memory in a multi-processor computer system is provided which is capable of (1) detecting when one of a set of predefined data inconsistency states occurs as a data transaction request is being processed, and (2) correcting the data inconsistency states so that the operation may be executed in a correct and consistent manner.

Abstract: A system control unit (SCU), adapted to operating a plurality of central processor units (CPUs) in a parallel fashion in combination with at least one input/output (I/O) unit and for allowing the CPUs and I/O units to controllably access address segments of a system memory, arbitrates communication requests received at the SCU ports from the CPUs and I/O units in such a manner that available system resources are optimally used, while at the same time guaranteeing that all requests are granted within a reasonable period of time. Incoming communication requests are stored, and from there these incoming communication requests are selected, on the basis of a pre-defined prioritizing scheme, commands corresponding to requests that are to be arbitrated. For the command corresponding to each request selected for being arbitrated, there is generated a first vector defining all system resources that are required for executing the command.

Abstract: For efficiently handling data transactions between various system units (CPUs, I/O units and main memory units) in a multi-processor system, the system units are linked via a plurality of expandable crossbar modules, each providing a set of interconnections or well-defined mappings between the sets of input and output nodes, with each output being defined in terms of only one input. In addition to the nodes provided at the input and output sections, each crossbar module is also provided with discrete input and output expansion portions through which the module may be linked to other identically configured crossbar modules when additional nodes are to be integrated into the system. The expansion ports allow serial linking of crossbar modules so as to establish a connection between source and destination nodes which are spread across different crossbar modules.