Abstract: A fault tolerant computer system includes at least two central processing units each having a cache memory and a parity error detector adapted to sense parity errors in blocks of information read from and write to cache and to issue a cache parity read or write error flag if a parity error is sensed. A system bus couples the CPU to a System Control Unit having a parity error correction facility, and a memory bus couples the SCU to a main memory. An error recovery control feature distributed across the CPU, including a Service Processor and the operating system software, is responsive to the sensing of a read parity error flag in a sending CPU and a write parity error flag in a receiving CPU in conjunction with a siphon operation for transferring the faulting block from the sending CPU to main memory via the SCU (in which given faulting block is corrected) and for subsequently transferring the corrected memory block from main memory to the receiving CPU when a retry is instituted.

Abstract: A collector for the results of a pipelined central processing unit of a digital data processing system. The processor has a plurality of execution units, with each execution unit executing a different set of instructions of the instruction repertoire of the processor. The execution units execute instructions issued to them in order of issuance by the pipeline and in parallel. As instructions are issued to the execution units, the operation code identifying each instruction is also issued in program order to an instruction execution queue of the collector. The results of the execution of each instruction by an execution unit are stored in a result stack associated with each execution unit. Collector control causes the results of the execution of instructions to program visible registers to be stored in a master safe store register in program order which is determined by the order of instructions stored in the instruction execution stack on a first-in, first-out basis.

Abstract: Apparatus and method for a supervisor for data processing system capable of utilizing a plurality of operating systems. The supervisor includes apparatus for identifying a condition in the data processing system requiring a different operating system. A reserved memory area associated with the currently active operating system is then addressed and register contents of a central processing unit are stored in the reserved memory area. The reserved memory of the operating system being activated is addressed and causes the address of the reserved memory of the operating system being activated, the data related to permitting the physical memory associated with the operating system being activated, contents of registers safestored in the reserve-memory and, data establishing the decor of the operating system being activated are entered in the central processing unit. The operating system to be activated is then enabled, and execution of permitted instructions by the second operating system is begun.

Abstract: Cache memory includes a dual or two part cache with one part of the cache being primarily designated for instruction data while the other is primarily designated for operand data, but not exclusively. For a maximum speed of operation, the two parts of the cache are equal in capacity. The two parts of the cache, designated I-Cache and O-Cache, are semi-independent in their operation and include arrangements for effecting synchronized searches, they can accommodate up to three separate operations substantially simultaneously. Each cache unit has a directory and a data array with the directory and data array being separately addressable. Each cache unit may be subjected to a primary and to one or more secondary concurrent uses with the secondary uses prioritized.

Abstract: A central processor for a general-purpose digital data processing system. The processor has a pair of caches, an operand cache for operands and an instruction cache for instructions, as well as a plurality of execution units, where each execution unit executes a different set of instructions of the instruction repertoire of the central processor. An instruction fetch unit fetches instructions from the instruction cache and stores them in an instruction stack. The central pipeline unit which has five stages obtains instructions of a given program in program order from the instruction stack of the instruction fetch unit.

Abstract: A method and a central execution pipeline unit for initiating the execution of instructions of a synchronous central processor unit (CPU) of a general-purpose digital data processing system. Instructions containing address information and an instruction field are obtained in program order from an instruction fetch unit of the CPU. In a first stage, requiring one clock period, the address information of an instruction is utilized to form the carrys and sums of an effective address and to initiate the formation of a virtual address. Concurrently, the instruction field is decoded to produce memory command signals and data alignment signals. In a second stage, the formation of the effective and virtual addresses initiated in the first stage is completed, and the word address portion of the virtual address is transmitted to the cache unit of the CPU.

Abstract: This relates to an apparatus for performing single error correction, double error detection of binary words, each section of the apparatus processing one byte of raw data. Each section includes first logic means for producing a first plurality of intermediate sector matrix parity outputs. A second logic means receives one of the first plurality of intermediate sector matrix parity outputs and a second plurality of intermediates matrix parity outputs from other sections and generates therefrom a syndrome signal. A third logic means receives this syndrome signal and syndrome signals from other sections and generates therefrom the corrected data bits.