What is the principle of von Neumann's architecture? How does von Neumann's machine work?

Today it is difficult to believe, but computers, without which many can no longer imagine their lives, appeared only some 70 years ago. One of those who made a decisive contribution to their creation was the American scientist John von Neumann. He proposed the principles on which most computers still operate today. Consider how the von Neumann machine works.

Brief biographical note

Janos Neiman was born in 1930 in Budapest, in a very wealthy Jewish family, who later managed to get the title of nobleman. He was distinguished from childhood with outstanding abilities in all fields. At the age of 23, Neiman had already defended his Ph.D. thesis in experimental physics and chemistry. In 1930, a young scientist was invited to work in the US, at Princeton University. Simultaneously, Neiman became one of the first employees of the Institute for Advanced Studies, where he worked as a professor until the end of his life. Neumann's scientific interests were quite extensive. In particular, he is one of the creators of the mathematics of quantum mechanics and the concept of cellular automata.

Contribution to Informatics

Before we find out which principle does not correspond to von Neumann's architecture, it will be interesting to learn how the scientist came to the idea of creating a modern-type computer.

Being an expert in the field of mathematics of explosions and shock waves, in the early 1940s von Neumann was a scientific consultant in one of the laboratories of the United States Army Ammunition Office. In the autumn of 1943, he arrived in Los Alamos to participate in the development of the Manhattan Project at the personal invitation of his leader, Robert Oppenheimer. Before him was the task of calculating the force of implosion compression of the atomic bomb charge to the critical mass. To solve it, large calculations were required, which at first were carried out on hand calculators, and later on mechanical tabulators of IBM, using punch cards.

Von Neumann got acquainted with information on the progress of the creation of electronic-mechanical and fully electronic computers. Soon he was involved in the development of computers EDVAC and ENIAC, as a result of which he began to write the work "The first draft report on EDVAC", the remaining unfinished, in which he presented to the scientific community a completely new idea of what a computer architecture should be.

Von Neumann's Principles

Informatics as a science by the year 1945 was at a deadlock, as all computers stored in their memory processed numbers in the 10th form, and programs for performing operations were set by installing jumpers on the patch panel.

This greatly limited the capabilities of computers. A real breakthrough became the principles of von Neumann. Briefly, they can be expressed in one sentence: the transition to a binary number system and the principle of a stored program.

Analysis

Let's consider, on what principles the classical structure of the von Neumann machine is based, in more detail:

1. Transition to binary system from decimal

This principle of the Neumann architecture allows us to use rather simple logic devices.

2. Software control of an electronic computer

The operation of the computer is controlled by a set of instructions executed successively one after another. The development of the first machines with a program stored in memory laid the foundation for modern programming.

3. Data and programs in the computer's memory are stored together

In this case, both the data and the program commands have the same way of writing in the binary system, so in certain situations, it is possible to perform the same actions as above on the data.

Consequences

In addition, the architecture of the Fonnemann machine has the following features:

1. Memory cells have addresses that are numbered sequentially

Thanks to the application of this principle, it became possible to use variables in programming. In particular, at any time you can refer to a particular memory location at its address.

2. The possibility of a conditional transfer during program execution

As already mentioned, the commands in the programs must be executed sequentially. However, it is possible to make a transition to any area of the code.

How von Neumann's machine works

Such a mathematical model consists of a memory (ZU), arithmetic logic unit (ALU), a control device, as well as input and output devices. All program instructions are written in memory cells located in the neighborhood, and the data for their processing is in arbitrary cells.

Any team should consist of:

• Specify which operation should be performed;
• Addresses of memory cells in which the original data affected by the specified operation is stored;
• Addresses of cells to which the result should be written.

The operations indicated by the commands on specific initial data are performed by the ALU, and the results are written in memory cells, i.e., stored in a form convenient for subsequent machining, or transmitted to the output device (monitor, printer, etc.) and available to the person.

CU controls all parts of the computer. From it to the other devices receive signals-orders "what to do", and from other devices it receives information about what state they are in.

The control device has a special register called the "command counter" of the SC. After loading the source data and the program into the memory, the SC writes the address of its 1st command. The UC reads the contents of the cell from the computer's memory, whose address is in the SC, and places it in the "Command Register". The control device determines the operation corresponding to a specific command, and "marks" in the computer's memory the data whose addresses are indicated in it. Further, the ALU or the computer hardware proceeds to the operation, after which the contents of the SC are changed to one, i.e., indicates the next command.

Criticism

The shortcomings and modern perspectives of von Neumann architecture continue to be the subject of discussions. The fact that the machines created on the principles advanced by this outstanding scientist are not perfect was noticed a very long time ago.

Therefore, in exam tickets on computer science one can often find the question "what principle does von Neumann's architecture do not correspond to and what disadvantages does it have."

When answering its second part, it is necessary to indicate:

• For the presence of a semantic gap between high-level programming languages and the command system;
• On the problem of matching the OP and the bandwidth of the processor;
• On the emerging software crisis, caused by the fact that the cost of its creation is much lower than the cost of hardware development, and there is no possibility of full testing the program;
• The lack of prospects in terms of speed, since its theoretical limit has already been reached.

As to which principle does not correspond to von Neumann's architecture, then we are talking about the parallel organization of a large number of data streams and commands inherent in a multiprocessor architecture.

Conclusion

Now you know what the von Neumann architecture does not correspond to. Obviously, science and technology do not stand still, and, perhaps very soon, computers of a completely new type will appear in every house, thanks to which humanity will reach a new level of its development. By the way, prepare for the exam will help the training program "Architecture von Neumann." Such digital educational resources facilitate the learning of the material and provide an opportunity to evaluate your knowledge.