Topic: von Neumann computer

Summary

Almost all computers share the structure developed by von Neumann and originally specified by Charles Babbage: a central store, a computation unit, input/output ports, and a program counter for sequential access of programs stored in memory. Von Neumann added the concepts of stored programs and self-modification. The later has been replaced by index registers. Most machines include interrupt handling and control traps.

Most high-level languages are modeled on 'von Neumann' machines. They use variables and data objects as the memory store, arithmetic operators defined for computation, and 'go to's or control structures for determining the program's execution.

Advantages-- Simple conversion from spatial representation to sequential processing. Widely used in many applications. (cbb 5/80)

Note von Neumann's references to artificial neurons. The history of his idea is as follows: Turing developed his universal model for computation in 1936. McCulloch and Pitts developed their artificial neuron in 1943 and proved that it was equivalent to a Turing machine. They felt that this would solve the problem of mind. von Neumann realized that a vacuum tube could efficiently implement the McCulloch and Pitts model. The speed would be many times that of actually neurons. The one difference would be synchronous instead of asynchronous behaviour. Because of the tie back to Turing machines, the architecture implements a universal computing machine. (cbb 4/94)

Subtopic: design principles

Quote: an electronic computing machine should use the binary system and convert to decimal only for I/O

Quote: a computer should be as simple as possible and avoid simultaneous operations as done by existing devices (e.g., add) [»vonnJ6_1945]

Quote: von Neumann enunciated the basic principles for designing an electronic computing machine [»utleAM6_1949]

Subtopic: control/arithmetic unit

Quote: a computer has a control function that carries out its instructions [»vonnJ6_1945]

Quote: a computer has a central arithmetical part for addition, subtraction, multiplication and division [»vonnJ6_1945]

Quote: the orders or code words for a computer fall into four classes: arithmetic, data movement, control transfer, and input/output [»vonnJ6_1945]

Subtopic: index instructions

Quote: a computer can modify the address component of an order; earlier computers used fixed address instructions [»vonnJ6_1945]

Subtopic: memory

Quote: a computer needs a considerable, universal memory for partial results, programs, tables, numeric data, and data to be sorted [»vonnJ6_1945]

Quote: a high-speed computer should use memory instead of the outside recording mediums that existing computing devices use [»vonnJ6_1945]

Subtopic: I/O

Quote: a computer has input and output parts which transfer data between memory and the outside recording medium [»vonnJ6_1945]

Subtopic: correspondance with neurons

Quote: a computer's arithmetic, control and memory parts correspond to associative neurons; input/output corresponds to sensory and motor neurons [»vonnJ6_1945]

Quote: digital computers use relay-like elements of two or more states; e.g., neurons which can be imitated by vacuum tubes at 1000x faster [»vonnJ6_1945]

Quote: build a computer from abstract neurons; will be implemented by vacuum tubes [»vonnJ6_1945]

Quote: an E-element models a MacCulloch/Pitts neuron; fixed synaptic delay for synchronous operation, thresholds 1,2,3 and absolute inhibition [»vonnJ6_1945]

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