Abstract: In order to gather, store temporarily and deliver (if needed) central processor safestore information, a multiphase clock is employed to capture (one full clock cycle behind) the safestore information which typically includes all software visible registers in all (or selected) data manipulation chips of the CPU by routing the safestore information through temporary storage (under the influence of the multiphase clock) in a cache data array and into a special purpose XRAM module. Thus, upon the sensing of a fault, valid safestore information is available in the XRAM for analysis and, if appropriate, resumption of operation at a sequential point just previous to that at which the fault occurred.

Abstract: In order to provide efficient error detection in a central processor's Basic Processing Unit (BPU) including an AX (address and execution) module, a DN (decimal numeric) module and an FP (floating point) module, each module is provided redundantly in a master/slave pair, and the local result of data manipulation operations performed in each pair are compared for identity before the results are validated for subsequent use in the central processor.

Abstract: In a Central Processing Unit (CPU) incorporating a Basic Processing Unit (BPU) which includes an address and execution (AX) unit, a decimal numeric (DN) unit and a floating point (FP) unit and also incorporating a cache unit situated logically intermediate the BPU and system memory, BPU data manipulation errors are sensed by duplicating each of the AX, DN and FP chips (i.e., duplicating the BPU) and performing all BPU data manipulation operations redundantly. The outputs from the duplicate BPUs are placed on respective master (MRB) and slave (SRB) result busses which are coupled to the cache unit, and the results are compared, byte-by-byte in the cache unit. If the results are not identical in each byte of the result, the individual chip handling the byte in the cache unit and detecting the no-compare condition issues an individual error signal, and appropriate steps to remedy or otherwise respond to the error signal may be undertaken within the cache unit, within the CPU and within the system.

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: In a computer system, a memory system has a memory structure and means whereby the smallest memory unit, the RAM chip, may be addressed and accessed twice during each clock cycle.

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: Method and apparatus for prefetching instructions for a pipelined central processor unit for a general purpose digital data processing system. A table is maintained for purposes of predicting the target addresses of transfer and indirect instructions based on past history of the execution of those instructions. The prefetch mechanism forms instruction addresses and fetches instructions in parallel with the execution of previously fetched instructions by a central execution pipeline unit of the central processor unit. As instructions are prefetched, the transfer and indirect prediction (TIP) table is checked to determine the past history of those instructions. If no transfers or indirects are found, the prefetch proceeds sequentially. If transfer or indirect instructions are found, then the prefetch uses information in the TIP table to begin fetching the target instruction(s).

Abstract: An improved multiword data register array which features RAM technology to provide a greater memory capacity in a smaller space than a conventional register arrays. Whereas RAM technology does not ordinarily include the capability of simultaneously reading and writing, in accordance with the present invention, data may be written into the register on a first half cycle of a clock signal and read out of memory on the second half cycle of the same clock signal. If the writing and the reading of the data relate to the same address in the register array, the data may be read directly from the input circuit.

Abstract: A 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: Method and apparatus for calculating the residue of a signed binary number of "n" bits with respect to a given check base m where m=2.sup.b -1. The bits of the binary number excluding the sign bit are partitioned into number segments, each of b bits starting with the least significant bit. If (n-1) is not an even multiple of b, higher order bit positions of the number segment containing the next most significant bit of the binary number are filled with logical zeros. A sign segment of b bits is formed. Both number and sign segments have boundaries. The bit position in the sign segment relative to a sign segment boundary which corresponds to the bit position of the sign bit "s" relative to the nearest boundary of a number segment is filled with a logical zero. All other bit positions of the sign segment are filled with the sign bit. The number and sign segments are applied to carry save adders to reduce the number segments and sign segment to a single sum segment and a single rotated carry segment.

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 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: A clock pulse driver has applied to it a system clock pulse signal, or system clock and produces a first set of individually enabled clock pulse signals, the leading edges of the pulses of which substantially coincide with the leading edges of the pulses of the system clock, a second set and a third set of clock pulse signals, the trailing edges of the pulses of which substantially coincide with the leading edges of the pulses of the system clock. The width of the pulses of the three sets of output signals are controllable by first, second and third delay pulse signals. The clock pulse driver also produces delay signals the pulses of which have a predetermined relationship to the pulses of the system clock which delay signals can be used to control the widths of the first, second and third sets of clock signals produced by the driver circuits, and to control the delay or offset of the first, second and third sets of clock signals produced by the driver circuit.

Abstract: A one's complement adder for adding two binary numbers A.sub.i, B.sub.i in the one's complement system is constructed from a conventional adder circuit by connecting the generate output signal G produced by the adder to the carry-in terminal of the adder. The value of the generate signal is independent of the signal applied to the carry-in terminal which prevents the adder from exhibiting sequential or indeterminate behavior.