Abstract: A data processing system including an addressable main memory for storing data and directly executable microinstructions, and a central processing chip having a data interface terminal and an instruction terminal. A processor memory bus is connected between the main addressable memory and the central processing chip data interface terminal. An instruction bus is connected between the central processing chip instruction terminal and the addressable memory.The directly executable microinstructions in the addressable main memory are fetched from the main memory by an apparatus which includes an instruction address circuit connected to the processor memory bus and the instruction bus. The instruction address circuit includes a virtual address register circuit for receiving a portion of a virtual address from the instruction bus, and a portion of the mentioned virtual address from the processor memory bus.

Abstract: In a data handling system having one or more processors, a cache memory associated with each processor and a main memory unit, each cache memory is divided into an equal number of portions, and the main memory is divided into a corresponding number of portions. A data transfer bus is provided between each group of cache memory portions and the corresponding portion of main memory such that each group of cache memory portions corresponds to only a portion of main memory. Each data transfer bus in independently controlled such that the rate of data transfers for the system as a whole is increased.