In the late 1960s and early 1970s, significant improvements in unipolar semiconductor technologies made it possible to produce circuits with more than 1000 transistors on a single structure. The story of the creation of the first large-scale integrated circuit, called a microprocessor, began in 1969. It was then that the Japanese calculator company Busicom ordered from the American company Intel a set of microchips to assemble calculators with different capabilities. At that time, Intel had already gained a lot of experience in the production of memory chips, which were supplied to manufacturers of various computer systems. The result of the Intel specialists, led by Marcian E. Hoff, was not only the construction of the ordered set of chips, but also the production of the first microprocessor marked 4004 in 1971. 
[001] Intel 4004 microchip. This was a chip containing the entire processor of a computer system. The 4004 microprocessor, made in p-MOS technology, consisted of nearly 2300 transistors. The microprocessor was accompanied by three other microchips;
4001 containing 256 bytes (byte = 8 bits) of Read Only Memory (ROM) and a 4-bit input-output port, 4002 containing four 20-digit registers and a 4-bit output port, 4003 containing a 10-bit shift register into which data could be input and output serially. These four chips formed the MCS - 4 - microcomputer system with capabilities comparable to those of the first ENIAC computer. With the appearance of the first microprocessor, the race to build ever more powerful and faster processor chips began. The 4004 microprocessor was 4-bit, meaning that information inside and outside the chip is processed and transmitted in 4-bit portions. This was a great limitation to the speed of the microprocessor, so it was natural for the designers to expand the unit of information transmitted once, first to 8, then to 16, and recently to 32 and 64 bits. 
[002] Architecture of the Intel 4004 microchip. In the mid-seventies, the 8-bit Intel microprocessor with the symbol 8080 became the most popular microprocessor in the world. It became a reference design and was copied and improved by many companies (e.g. Z-80 by Zilog).
Figure [003] presents a general diagram of the microprocessor architecture, which practically corresponds to the srchitecture of any processor controlled by a program in memory (the so-called von Neumann architecture), including the 8O8O microprocessor. The microprocessor consists of four functional blocks. These blocks are: 
[003] Microprocessor architecture diagram. 1 - control block, 2 - register block, 3 - arithmetic-logic unit block, 4 - data bus, 5 - data buffer, 6 - command register, 7 - command decoder, 8 - command cycle controller, 9 - control bus, 10 - register selection, 11 - register set, 12 - command counter, 13 - accumulator, 14 - summator, 15 - conditions, 16 - address bus, 17 - address buffer, 18 - data bus, 19 - address bus. The main function of the control block is to interpret the commands retrieved from the memory located outside or sometimes within the processor (so-called single-chip microcomputers), and then on this basis to control the internal operation of the microprocessor and respond to signals arriving from outside and produce signals to organize the microprocessor's cooperation with other elements of the system, such as memory and input-output systems. Microprocessors have the ability to interpret from a few dozen to two hundred commands of varying complexity (e.g. the 8080 command list contains 72 commands). The basic element of the arithmetic-logic unit (ALU) block is a summator, whose capabilities affect the processing capacity of the entire microprocessor. Even for 8-bit microprocessors these capabilities were small, because arithmetic and logical operations concerned only 8-bit binary numbers. 
[004] Simulation of the functioning of the 4004 processor. The register block of almost every microprocessor contains general purpose registers, which are used to store some temporary data, and specialized registers, which support some specific functions of the
microprocessor, such as controlling the sequence of executed program commands (e.g., command counter register - PC) or addressing data in memory (e.g., index registers, indirect addressing, stack pointer). From the form of the registers block it is easy to see if the microprocessor is suitable for general applications or if it is better for specific applications. These functional blocks of the microprocessor are interconnected via internal transfer buses whose size, expressed by the number of bits of information transferred in parallel, helps us classify the microprocessor into the appropriate category from 1 to 64 bits. 
[005] Diagram of a microcomputer system. Of course, such a microprocessor cannot operate in a vacuum. It must interact with the various types of memory that hold programs and data, and it must interact with the input-output devices that are used to input changing data and output the results in processing. To this end, all microprocessor companies surround microprocessors with many large-scale integration circuits performing various functions, some of which are even
more complex than the processor itself. Figure 5 shows a diagram of a microcomputer system and the interrelationship of the microprocessor with memory and input-output microcircuits. What differentiates microcomputer systems from traditional systems is precisely the precise division of system functions, which are now carried out by individual electronic circuits of large-scale integration, and the clear delineation of information transfer paths within the system in the form of so-called address, data and control buses.
The concept of buses was borrowed from minicomputer systems, but in relation to microcomputer systems it is developed and unified. 
[006] Layout of the Intel 8008 microchip. The popularisation of microprocessors and the microcomputer systems built on them encountered numerous difficulties until the mid-1970s. They were used mainly to replace non-programmable logic circuits and in consumer equipment such as radios, TV sets, washing machines and microwave ovens, where they were not visible to the user. • • •
|
