Abstract: A data system architecture is described that allows multiple processing and storage resources to be connected to multiple clients so as 1) to distribute the clients' workload efficiently across the available resources; and 2) to enable scaleable expansion, both in terms of the number of clients and in the number of resources. The major features of the architecture are separate, modular, client and resource elements that can be added independently, a high-performance cross-bar data switch interconnecting these various elements, separate serial communication paths for controlling the cross-bar switch settings, separate communication paths for passing control information among the various elements and a resource utilization methodology that enables clients to distribute processing or storage tasks across all available resources, thereby eliminating “hot spots” resulting from uneven utilization of those resources.

Abstract: A data system architecture is described that allows multiple processing and storage resources to be connected to multiple clients so as 1) to distribute the clients' workload efficiently across the available resources; and 2) to enable scaleable expansion, both in terms of the number of clients and in the number of resources. The major features of the architecture are separate, modular, client and resource elements that can be added independently, a high-performance cross-bar data switch interconnecting these various elements, separate serial communication paths for controlling the cross-bar switch settings, separate communication paths for passing control information among the various elements and a resource utilization methodology that enables clients to distribute processing or storage tasks across all available resources, thereby eliminating “hot spots” resulting from uneven utilization of those resources.

Abstract: Apparatus for maintaining duplicate copies of information stored in fault-tolerant computer main memories is disclosed. A non write-through cache memory associated with each of the system's processing elements stores computations generated by that processing element. At a context switch, the stored information is sequentially written to two separate main memory units. A separate status area in main memory is updated by the processing element both before and after each writing operation so that a fault occurring during data processing or during any storage operation leaves the system with sufficient information to be able to reconstruct the data without loss of integrity.To efficiently transfer information between the cache memory and the system main memories without consuming a large amount of processing time at context switches, a block status memory associated with the cache memory contains an entry for each data block in the cache memory.

Abstract: A multi-processor computer system is disclosed in which processing elements, memory elements and peripheral units can be physically added and removed from the system without disrupting its operation or necessitating any reprogramming of software running on the system. The processing units, memory units and peripheral units are all coupled to a common system bus by specialized interface units. The processing elements are organized into partially independent groups each of which has dedicated interface units, but the processing units share system resources including peripherals and the entire memory space. Within each processing element group at any one time, group supervisory tasks are performed by one of the processors, but the supervisor function is passed among the processors in the group in a sequence to prevent a fault in one processor from disabling the entire group. Communication between groups is accomplished via the common memory areas.

Abstract: Circuitry for a fault-tolerant computer is disclosed which circuitry is constructed in two identical halves. Each half, by itself, is not a functionally-complete circuit, however, the two identical halves can be connected together to provide a functionally-complete circuit. Each of the two circuit halves is considerably less complex than a functionally-complete circuit yet, when connected together, the two halves provide fault detection capabilities equivalent to a computer system in which the outputs of two functionally-complete, redundant circuits are compared to detect faults.In particular, each inventive circuit half contains a complete data processing and control unit but only one half of the memory which is necessary for a functionally-complete unit. The processing units on each circuit half operate simultaneously on identical data and the same address information is provided to the memories on each circuit half.

Abstract: A multi-processor computer system is disclosed in which processing elements, memory elements and peripheral units can be physically added and removed from the system without disrupting its operation or necessitating any reprogramming of software running on the system. The processing units, memory units and peripheral units are all coupled to a common system bus by specialized interface units. The processing elements are organized into partially independent groups each of which has dedicated interface units, but the processing units share system resources including peripherals and the entire memory space. Within each processing element group at any one time, group supervisory tasks are performed by one of the processors, but the supervisor function is passed among the processors in the group in a sequence to prevent a fault in one processor from disabling the entire group. Communication between groups is accomplished via the common memory areas.