MICROPROGRAMMED PROCESSOR WITH VARIABLE BASIC MACHINE CYCLE LENGTHS

A microprogrammed processor has a single storage unit for both main store and control store wherein the read/write times of the storage unit are less than the time required for the microprogram controlled hardware to execute a control word. Since there is no requirement for the hardware to wait for a next succeeding access to storage as in typical known processors, but rather the storage unit now waits for the hardware, it becomes feasible and practicable to improve the performance of the processor significantly with little additional cost by providing basic machine cycle times for different control word executions which are maintained at a minimum. In the preferred embodiment, a decode circuit examines each control word after it is transferred from control store to a control register to determine the word type which is to be executed. Depending upon the word type, the decode circuitry applies control pulses to the processor clock to cause ti to produce a selected one of three available cycle lengths or a combination of two of said three available cycle lengths. In this manner, system performance is significantly improved.