System Design of a Small, Fast Digital Computer

In this paper the system design of a 250 Mc tunnel-diode computer is presented. To resolve the disparity between the obtainable arithmetic and main memory speeds, a sophisticated advanced control is used. The advanced control fetches instructions and operands from the main memory before they are actually needed by the arithmetic unit. These instructions and operands are stored in two small, high-speed tunnel-diode memories which are called queues. A third queue, the Storage Access Queue, is used for saving a storage access request if it cannot be serviced immediately. Hence, advanced control is split into four parts, the Instruction, Operand, Store and Arithmetic Controls, which operate independently (except for appropriate interlocks) of one another. In the design of any computing system which has advanced control, care must be taken to prevent the old value of a memory location from being used instead of a recently computed value. The proposed system insures that the latter is always used and in this respect the system appears as a conventional computer to the user. However, the system is not entirely conventional in its appearance; the use of a stack in place of the accumulator in the arithmetic unit is proposed. The arithmetic, modifier and input-output units are all designed to operate independently of one another and execute simple algorithms at high speeds. This permits the system to be built with an estimated 12,000 tunnel diodes and four 8000 word sections of memory. The system is expected to operate at very high speeds.