Abstract: An interface circuit for coupling a data handling unit with a memory unit having control inputs, an address signal input, a data signal input, and a data signal output is described. The interface circuit comprises an address buffer having an input and an output, said input receiving an address signal from said data handling unit, a first multiplexer which couples said memory unit with either said output of said address buffer or with said address signal, a data buffer having an input and an output, said input receiving a data signal from said data handling unit and said output being coupled with said memory data input, a second multiplexer for selecting either said memory data signal output or said data buffer output, and a comparator for comparing said address signal with the signal from said address buffer output, generating a control signal which controls said second multiplexer.

Abstract: A data processing unit is disclosed with a register file having a plurality of registers. A memory having a plurality of n-bit input/output ports, and a coupling unit for coupling the memory with the register file, a memory address and select unit for addressing the memory banks are provided. The coupling unit comprises a bus having a bus width of at least 2n-bits forming at least a first and second sub-bus, first couplers for coupling each memory bank or the register file selectively with one of the sub-busses, and second couplers for coupling the register file or the memory banks with the bus.

Abstract: A data processing unit is disclosed with a register file having a plurality of registers. A memory having a plurality of n-bit input/output ports, and a coupling unit for coupling the memory with the register file, a memory address and select unit for addressing the memory banks are provided. The coupling unit comprises a bus having a bus width of at least 2n-bits forming at least a first and second sub-bus, first couplers for coupling each memory bank or the register file selectively with one of the sub-busses, and second couplers for coupling the register file or the memory banks with the bus.

Abstract: A data processor is disclosed which comprises a first pipeline for decoding and executing data instructions, a second pipeline for decoding and executing address instructions, a unit for issuing multiple instructions to the pipelines, a first set of registers being coupled with the first pipeline, and a second set of registers being coupled with the second pipeline, wherein first and second pipeline process data in parallel.

Abstract: A computer system having a cache memory subsystem which allows flexible setting of caching policies on a page basis and a line basis. A cache block status field is provided for each cache block to indicate the cache block's state, such as shared or exclusive. The cache block status field controls whether the cache control unit operates in a write-through write mode or in a copy-back write mode when a write hit access to the block occurs. The cache block status field may be updated by either a TLB write policy field contained within a translation look-aside buffer entry which corresponds to the page of the access, or by a second input independent of the TLB entry which may be provided from the system on a line basis.

Abstract: A computer system having a cache memory subsystem which allows flexible setting of caching policies on a page basis and a line basis. A cache block status field is provided for each cache block to indicate the cache block's state, such as shared or exclusive. The cache block status field controls whether the cache control unit operates in a write-through write mode or in a copy-back write mode when a write hit access to the block occurs. The cache block status field may be updated by either a TLB write policy field contained within a translation look-aside buffer entry which corresponds to the page of the access, or by a second input independent of the TLB entry which may be provided from the system on a line basis.

Abstract: Methods and apparatus are disclosed for realizing an integrated cache unit (ICU) comprising both a cache memory and a cache controller on a single chip. The novel ICU is capable of being programmed, supports high speed data and instruction processing applications in both Reduced Instruction Set Computers (RISC) and non-RISC architecture environments, and supports high speed processing applications in both single and multiprocessor systems. The preferred ICU has two buses, one for the processor interface and the other for a memory interface. The ICU support single, burst and pipelined processor accesses and is capable of operating at frequencies in excess of 25 megahertz, achieving processor access times of two cycles for the first access in a sequence, and one cycle for burst mode or piplined accesses. It can be used as either an instruction or data cache with flexible internal cache organization.

Abstract: Methods and apparatus are disclosed for supporting the caching of interlock variables in cache memory units employed in multiprocessor and/or multitasking environments. The preferred embodiment of the invention includes methods and apparatus for selectively treating interlock variables as cachable or non-cachable. The disclosed methods and apparatus are suitable for supporting high speed data and instruction processing applications in both RISC and non-RISC architecture environments, can be integrated on a single chip and allows for better performance and utilization of the computer system bus structure since most of the interlock variable accesses are faster and do not appear on the memory bus (only in the cache).

Abstract: Methods and apparatus are disclosed for realizing an integrated cache unit which may be flexibly used for cache system design. The preferred embodiment of the invention comprises both a cache memory and a cache controller on a single chip. In accordance with an alternative embodiment of the invention, the cache memory may be externally located. Flexible cache system design is achieved by the specification of desired cache features through the setting of appropriate cache option bits. The disclosed methods and apparatus support this user oriented approach to flexible system design. The actual setting of option bits may be performed under software control and allows a high performance cache system to be designed with few parts, at low cost and with the ability to perform with high efficiency.

Abstract: A streamlined instruction processor processes data in response to a program composed of prespecified instructions in pipeline cycles. The processor comprises an instruction fetch unit, including an instruction interface adapted for connection to an instruction memory and for fetching instructions from the instruction memory. The instruction fetch unit includes an instruction prefetch buffer coupled to the instruction interface for buffering a sequence of instructions supplied to the instruction interface. A branch target cache is coupled with the prefetch buffer for storing sets of instructions retrieved from a corresponding set of locations in the instruction memory, having sequential instruction addresses. The first instruction in each such set is a branch target instruction in the program.In addition, an execution unit including a data interface adapted for connection to the data memory, executes the instructions in pipeline cycles.

Abstract: Methods and apparatus for realizing a high performance interface between a processor, constituting part of a reduced instruction set computer (RISC) system, and a set of devices, including memory means. According to the invention, the interface includes three independent buses. A shared processor output bus, a processor input instruction bus, and a bidirectional data bus. The shared processor output address bus coupled the processor and the computer's memory. This bus carries both instructon and data access signals being transmitted by the processor to the memory. The processor input instruction bus also couples the processor and the computer's memory means, but carries instruction signals being transmitted from the memory to the processor. The bidirectional data bus provides a signal path for carrying data signals being transmitted by the memory to the processor and vice-a-versa.

Abstract: An integrated circuit includes an input clock generator circuit responsive to an external TTL level clock signal for generating an internal CMOS level system clock signal for its own use and for use by other integrated circuits. The integrated circuit also includes an internal clock generator circuit responsive to either the internal CMOS level system clock signal or an external CMOS level system clock signal for generating internal CMOS level phase clock signals for its own use. As a result, the integrated circuit has a higher speed of operation since the propagation delay between the CMOS level system clock signal and internal clock signals has been minimized.