Data processing apparatus and method employing instruction pipelining

摘要

A data processing system for processing a sequence of program instructions has two independent pipelines, an instruction pipeline and an execution pipeline. Each pipeline has a plurality of serially operating stages. The instruction stages read instructions from storage and form therefrom address data to be employed by the execution pipeline. The execution pipeline receives the address data and uses it for referencing stored data to be employed for execution of the program instructions. Both pipelines operate synchronously under the control of a pipeline control unit which initiates operation of at least one stage of the execution pipeline prior to completion of the instruction pipeline for a particular instruction. Thereby operation of at least one instruction stage and one execution stage of the respective pipelines overlap for each program instruction. The instruction and execution pipelines share high speed memory. The pipeline control unit can independently control the flow of instructions through the two pipelines. This is important for operation in conjunction with a microcode storage element which allows conditional branching and subroutine operation. Circuitry also detects pipeline collisions and exception conditions and delays or inhibits operation of one or more of the pipeline stages in response thereto. Under control of the pipeline control unit, one of the independent pipelines can operate while the other is halted.