# Von neumann architecture

## Table of Contents:

## John von Neumann (1903-1957)

John von Neumann (born Johann von Neumann) was a child prodigy, born into a banking family in Budapest, Hungary. When only six years old he could divide eight-digit numbers in his head. He received his early education in Budapest, under the tutelage of M. Fekete, with whom he published his first paper at the age of 18.

Entering the University of Budapest in 1921, he studied Chemistry, moving his base of studies to both Berlin and Zurich before receiving his diploma in 1925 in Chemical Engineering. He returned to his first love of mathematics in completing his doctoral degree in 1928. He quickly gained a reputation in set theory, algebra, and quantum mechanics. At a time of political unrest in central Europe, he was invited to visit Princeton University in 1930, and when the Institute for Advanced Studies (IAS) was founded there in 1933, he was appointed to be one of the original six Professors of Mathematics, a position which he retained for the remainder of his life.

In the second half of the 1930s the main part of von Neumann's publications, written partly in collaboration with F.J. Murray, was on "rings of operators" (now called Neumann algebras). Of all his work, these concepts will quite probably be remembered the longest. Currently it is one of the most powerful tools in the study of quantum physics. An important outgrowth of rings of operators is "continuous geometry." Von Neumann saw that what really determines the character of the dimensional structure of a space is the group of rotations that the structure allows. The groups of rotations associated with rings of operators make possible the description of space with continuously varying dimensions.

About 20 of von Neumann's 150 papers are in physics; the rest are distributed more or less evenly among pure mathematics (mainly set theory, logic, topological group, measure theory, ergodic theory, operator theory, and continuous geometry) and applied mathematics (statistics, numerical analysis, shock waves, flow problems, hydrodynamics, aerodynamics, ballistics, problems of detonation, meteorology, and two nonclassical aspects of applied mathematics, games and computers). His publications show a break from pure to applied research around 1940.

At the instigation and sponsorship of Oskar Morganstern, von Neumann and Kurt Gödel became US citizens in time for their clearance for wartime work. There is an anecdote which tells of Morganstern driving them to their immigration interview, after having learned about the US Constitution and the history of the country. On the drive there Morganstern asked them if they had any questions which he could answer. Gödel replied that he had no questions but he had found some logical inconsistencies in the Constitution that he wanted to ask the Immigration officers about. Morganstern strongly recommended that he not ask questions, just answer them!

During 1936 through 1938 **Alan Turing** was a visitor at the Institute and completed a Ph.D. dissertation under von Neumann's supervision. Von Neumann invited Turing to stay on at the Institute as his assistant but he preferred to return to Cambridge; a year later Turing was involved in war work at Bletc ar This visit occurred shortly after Turing's publication of his 1934 paper "On Computable Numbers with an Application to the Entscheidungs-problem" which involved the concepts of logical design and the universal machine. It must be concluded that von Neumann knew of Turing's ideas, though whether he applied them to the design of the I Machine ten years later is questionable.

During World War II, he was much in demand as a consultant to the armed forces and to civilian agencies. His two main contributions were his espousal of the implosion method for bringing nuclear fuel to explosion and his participation in the development of the hydrogen bomb.

Von Neumann's interest in computers differed from that of his peers by his quickly perceiving the application of computers to applied mathematics for specific problems, rather than their mere application to the development of tables. During the war, von Neumann's expertise in hydrodynamics, ballistics, meteorology, game theory, and statistics, was put to good use in several projects.

This work led him to consider the use of mechanical devices for computation, and although the stories about von Neumann imply that his first computer encounter was with the **ENIAC**. in fact it was with Howard Aiken's Harvard Mark I (ASCC) calculator. His correspondence in 1944 shows his interest with the work of not only Aiken but also the electromechanical relay computers of George Stibitz, and the work by Jan Schilt at the Watson Scientific Computing Laboratory at Columbia University. By the latter years of World War II von Neumann was playing the part of an executive management consultant, serving on several national committees, applying his amazing ability to rapidly see through problems to their solutions. Through this means he was also a conduit between groups of scientists who were otherwise shielded from each other by the requirements of secrecy. He brought together the needs of the Los Alamos National Laboratory (and the Manhattan Project) with the capabilities of firstly the engineers at the Moore School of Electrical Engineering who were building the ENIAC, and later his own work on building the IAS machine. Several "supercomputers" were built by National Laboratories as copies of his machine.

Postwar von Neumann concentrated on the development of the Institute for Advanced Studies (IAS) computer and its copies around the world. His work with the Los Alamos group continued and he continued to develop the synergism between computers capabilities and the needs for computational solutions to nuclear problems related to the hydrogen bomb.

Any computer scientist who reviews the formal obituaries of John von Neumann of the period shortly after his death will be struck by the lack of recognition of his involvement in the field. His Academy of Sciences biography, written by Salomon Bochner [1958], for example, includes but a single, short paragraph in ten pages - ". in 1944 von Neumann's attention turned to computing machines and, somewhat surprisingly, he decided to build his own. As the years progressed, he appeared to thrive on the multitudinousness of his tasks. It has been stated that von Neumann's electronic computer hastened the hydrogen bomb explosion on November 1, 1952." Dieudonné [1981] is a little more generous with words but appears to confuse the concept of the stored program concept with the wiring of computers: "Dissatisfied with the computing machines available immediately after the war, he was led to examine from its foundations the optimal method that such machines

should follow, and he introduced new procedures in the logical organization, the "codes" by which a fixed system of wiring could solve a great variety of problems."!

From the point of view of von Neumann's contributions to the field of computing, including the application of his concepts of mathematics to computing, and the application of computing to his other interests such as mathematical physics and economics, perhaps the most comprehensive is by Herman Goldstine [1972]. There has been some criticism of Goldstine's perspective since he personally was intimately involved in von Neumann's computing activities from the time of their chance meeting on the railroad platform at Aberdeen in 1944[2] through their joint activities at the Institute for Advanced Studies in developing the IAS machine.

There is no doubt that his insights into the organization of machines led to the infrastructure which is now known as the "von Neumann Architecture ". However, von Neumann's ideas were not along those lines originally; he recognized the need for parallelism in computers but equally well recognized the problems of construction and hence settled for a sequential system of implementation. Through the report entitled First Draft of a Report on the EDVAC [1945], authored solely by von Neumann, the basic elements of the stored program concept were introduced to the industry. A retrospective examination of the development[3] of this idea reveals that the concept was discussed by J. Presper Eckert, John Mauchly, Arthur Burks, and others in connection with their plans for a successor machine to the ENIAC. The "Draft Report" was just that, a draft, and although written by von Neumann was intended to be the joint publication of the whole group. The EDVAC was intended to be the first stored program computer, but the summer school at the Moore School in 1946 there was so much emphasis in the EDVAC that Maurice Wilkes, Cambridge University Mathematical Laboratory, conceived his own design for the EDSAC, which became the world's first operational, production, stn2ed-program computer.

In the 1950's von Neumann was employed as a consultant to review proposed and ongoing advanced technology projects. One day a week, von Neumann "held court" at 590 Madison Avenue, New York. On one of these occasions in 1954 he was confronted with the **FORTRAN** concept; John Backus remembered von Neumann being unimpressed and that he asked "why would you want more than machine language?" Frank Beckman, who was also present, recalled that von Neumann dismissed the whole development as "but an application of the idea of Turing's `short code'." Donald Gilles, one of von Neumann's students at Princeton, and later a faculty member at the University of Illinois, recalled in the mid-1970's that the graduates students were being "used" to hand assemble programs into binary for their early machine (probably the IAS machine). He took time out to build an assembler, but when von Neumann found out about he was very angry, saying (paraphrased), "It is a waste of a valuable scientific computing instrument to use it to do clerical work."

## Interesting Quotations

If people do not believe that mathematics is simple, it is only because they do not realize how complicated life is.

Anyone who considers arithmetical methods of producing random numbers is, of course, in a state of sin.

## Von Neumann Architecture for Computers

Von Neumann's contributions have been so widespread and so enduring because of his attitude towards his innovations. The foundations of his work were laid in the "First Draft of a Report on the EDVAC," written in the spring of 1945 and distributed to the staff of the Moore School of Engineering (engineering school of the University of Pennsylvania where the EDVAC was originally developed) in late June. It presented the first written description of the stored program concept and explained how a stored program computer process information.

The report organized the computer system into four main parts: the Central Arithmetical unit (CA), the Central Control unit (CU), the Memory (M), and the Input/Output devices (IO). The CA was to carry out the four basic arithmetic operations and perhaps higher arithmetical functions such as roots, logarithms, trigonometric functions, and their inverses. The CU was to control the proper sequencing of operations and make the individual units act together to carry out the specific task programmed into the system. The M was to store both numerical data (initial boundary values, constant values, tables of fixed functions) and numerically coded instructions. And the IO unit(s) were to serve as the user's interface into the computer.

Von Neumann was interested in presenting a "logical" description of the stored program computer rather than an engineering description. He was concerned with the overall structure of a computing system, the abstract parts that comprise it, the functions of each part, and how the parts interact to process the information. The specific materials or design of the implementation of the parts was not pertinent to his analysis. Any technology that meets the functional specifications can be used with no effect on his results. For instance, a person could take the place of the CC, a piece of paper the M, a calculator the CA, the keys and display of the calculator the I/O, resulting in a complete 'computer.'

Von Neumann's contributions to computer design were so wide spread not only because of his brilliance but also because of his attitudes. He was less concerned with patents and patent law then he was with spreading information about his innovations. Starting with his "First Draft" and continuing throughout his work in computers, von Neumann openly shared his thoughts and theories with anyone that was interested, including competitors. He openly and freely distributed his papers and gave talks on his latest ideas, changing the course of computers that were under development as his ideas evolved. Manufacturers went from building an EDVAC clone to building an EDSAC clone to building an IAS clone all on the basis of von Neumann's ideas.

His contributions endure even today: his basic architectural design can easily be recognized in the most advanced of today's computers.

## Bibliography

Aspray, William. __John Von Neumann and the Origins of Modern Computing__. Cambridge, Massachusetts: The MIT Press, 1990.

Hayes, John P. __Computer Architecture and Organization__. New York: McGraw-Hill Publishing Company, 1988.

Heims, Steve J. __John Von Neumann and Norbert Wiener: From Mathematics to the Technologies of Life and Death__. Cambridge, Massachusetts: The MIT Press, 1980.

Macrae, Norman. __John Von Neumann__. New York: Pantheon Books, 1992.