The fourth generation of computers 1974 - 1982

A new stage for the development of computers was the large integrated circuits (LSI). Element base of computers of the fourth generation is BIS. The rapid development of electronics, allowed to place on a single crystal thousands of semiconductors. This miniaturization has led to the emergence of low-cost computers. Small computers could fit on one desk. It was during these years that the term "personal computer" was born. Huge costly monsters disappear. Several dozens of users worked at once through one such computer, through terminals. Now. One person - one computer. The car was really personal.

Characteristics of the fourth generation computer

• Multiprocessing
• High level languages
• Computer networks
• Parallel and serial data processing

The first mini-computer is considered the DEC PDP-8 corporation. This machine was created to control a nuclear reactor. But it became popular in private manufacturing enterprises and in higher education. Its mass production began in 1965 and by the beginning of the 70s the number of these computers exceeded 100,000 units. An important transition from mini-computers to micro-computers is the creation of a microprocessor. Thanks to BIS, it became possible to place all the main elements of the CPU on a single chip. The first microprocessor was Intel-4004 created in 1971. It contained more than two thousand semiconductors, which are located on the same substrate. In one integrated circuit, the arithmetic is located - a logical device and a control device.

Altair-8800 is considered one of the first personal computers of the fourth generation. Created on the basis of the Intel-8080 microprocessor. Its appearance stimulated the growth of peripheral devices, high-level compilers.

Integrated circuits can be classified by the number of elements placed on a single chip:

• PIP - (Simple Integrated Circuits) up to 10 elements
• MIS - (Small Integrated Circuits) up to 100 elements
• SIS - (Average integrated circuits) up to 1 000 elements
• LSI - (Large integrated circuits) up to 10 000 elements
• VLSI - (Extra Large-Scale Integrated Circuits) Up to 1,000,000 Elements
• UBIS - (Ultra-large integrated circuits) up to 1,000,000,000 elements
• GBIS - (Gigabol integrated circuits) over 1 000 000 000 elements

A large integrated circuit is an advanced descendant of a simple integrated circuit. Which was one of the main elements of the previous generation. Large, it is called, not because the integrated circuit is large, but because it has a high degree of integration.

The process of manufacturing BIS is as follows. A photoresist photosensitive layer is applied above the crystal. Which is later illuminated above the template. After this negative show. Remove those areas that are lit. Impurities are introduced into the resulting gaps in the photoresist. After crystal annealing, similar operations are performed using different photomasks. Each template is responsible for the formation of a certain group of elements of the integrated circuit. In the final stage of LSI manufacturing, photo masks are used that form aluminum tracks to connect chains of complex configuration. BIS became one of the first electronics products that are only commercially available.

In the future, they began to produce software-controlled BIS. The functions of such a scheme vary depending on the program, which is also sprayed on a separate chip. This BIS consists of an operating unit and a program. Enter the program in the BIS, adjusts it to a specific class of tasks. The same integrated circuit can work both as an arithmetic unit and as a control unit.

The use of BIS has given a dramatic improvement in the basic indicators of speed and reliability. Such a high degree of integration, led to a decrease in the number of installation operations, reduced the number of external connections that were not initially reliable. This has greatly contributed to reducing the size, cost and increase reliability.

However, the emergence of BIS led to the emergence of problems. One of the main problems is the heat sink. The higher the degree of integration of the scheme, the higher the heat release. Requires constant cooling, without which the integrated circuit overheats and burns. There are also problems: interconnection of elements, control parameters. Large integrated circuits have already begun to be used in the third generation. System / 360 example.

Through research it was possible to create models of integrated circuits. Which work at a speed of several billion operations per second. When creating prototypes it turned out that it was impossible to put them into serial production. It turns out that with modern development of technology, achieving such speeds is impossible in general. And the problem is not in engineering solutions. And in the need to achieve absolutely pure chemical materials, crystal uniformity, stable temperature conditions. The interaction of electric fields inside the crystal.

In addition to changing the technical base of the fourth generation of computers, the direction of creation of these machines has changed. They were designed with the expectation of using high-level programming languages, many at the hardware level were designed for specific operating systems.

One of the most popular computers of the fourth generation is the IBM System / 370. Which, unlike its predecessor, the third generation of System / 360, had a more powerful system of micro-instructions and great low-level programming capabilities. In the System / 370 series machines, the virtual memory was programmatically implemented. When part of the disk space was allocated to use temporary data storage. Thus, the RAM was emulated. The end user had the impression that the machine had more resources than it actually is.

Technical characteristics of fourth-generation computers

• The use of modularity to create software
• Average signal delay 0.7 ns / gate
• For the first time, operating system modules began to be implemented at the hardware level.
• The basic element of RAM has become a semiconductor. Read write 100-150 ns.

The fourth generation of Soviet computers include: EU-1015, EU-1025, EU-1035, EU-1045, EU-1055, EU-1065. Personal computers that have become popular in everyday life: Electronics-85, Iskra-226, EU-1840, EU-1841, EU-1842. This generation also includes the Elbrus multiprocessor computer. Used in manufacturing and machine stations. Later he was replaced by "Elbrus-2". The computing power of this machine, for the fourth generation, was very high. It had about 64 megabytes of RAM, could perform up to 5 million floating point operations per second. Tire capacity up to 120 Mb / s.

Fourth-generation computers are of mass use. They are able to replace the previous generation of computers in all spheres of human activity. In the management of technological processes of enterprises, trade, engineering calculations, reference centers, traffic control, billing systems.