Introduction and evolution of Microprocessors


The modern era of devices be it the devices used in education, our home, to our offices, to inducstrial automation, transportation, medicine, or in defence etc are all microprocessor or microcontroller based systems. The most common of the is the desktop or the laptop are microprocessor based systems.

A microprocessor is an electronics programmable device that accepts the user input from memory or peripherals, processes it as per the instructions fetched from the memory and produces the result that can be stored back in memory or fed as input to other devices or applications.

The word microprocessor is made from two words micro and processor. Untill 1960 all systems were made usind discrete components which lead to very large and complex design, consume large amount of power, bulky and slow. It was only after the 1970s that the integration level in Ics increased to larger extent and thanks to the vLSI technology that the ICs size decreased ith increase in the component count on them thus making the size of the end products quite smaller.. This was used to miniaturize the Ics and hence the word micro and of course we are talking about the processing devive. These two words put together become the “microprocessor”. The microprocessor operates on binary numbers and understands the binary or so called the machine language.

Operation codes or in short “OPCODE” define the operation to be carried out on the binary operands. The opcodes are also supplied to the microprocessor in the language understood by it and that is the machine language. The codes are generally written in uman readable words called mnemonics and the converted to machine code by software called assember or hand coded by the programmer.

Microprocessor based system:

A microprocessor IC consist of the ALU, register sets, instruction decoder, a timing and contro units and some basic components for clock generation. Figure-1 shows a microcontroller based system.

Figure-1 consist of a CPU (generally a microprocessor), memory and other peripheral such as I/O units. CPU(Central Processing Unit) or also called as the microprocessor is the brain of the whole system all intefaced using the system external bus. The bus is the set of conductors used to carry address, data or control information and accordingly called as address bus, data bus and conrol bus. It does all arithmetic, logical operations and other operations as per the instructions supplied to it. It contains a set of registers such as general purpose registers, memory pointers, accumulators etc used during an operation. The instruction are decoded and necessary timing and control signals are genarted to synchronize and control the operations performed by different units. The memory is the primary and the secondary memory used to communicate with microprocessor and fetching and storing the instructions and the operands. The I/O are for allowing the user or human to interact with the system for example a keyboard allows user to type and send the operands or information to the microprocessor, a monitor for example allows us to view the output which may be in text, graphic or audio, video output.

Evolution of Microprocessors:

The evolution can be seen not from the era of invention of IC, but way back to 500 BC when abacus was invented in middle east and was the fastest calculating device untill in middle of 17th century. This was follwed by the invention of mechanical calculator that could add subtract, made up of gear wheel etc by Blaise Pascal in 1642 to help his father in tax-calculation. In 1971, Gottfried Wilhem Leibniz came up with an advanced version of this mechanical calculator, this could work faster than Pascal’s calculator and could be used for multiplication, division and square root etc. He also invented binary codes that could be used to represent any decomal number in binary code using only two digits a ‘0’ and a ‘1’.

George Boole, used the idea of Leibnitz and 1954 invented a new branch of mathematics called Boolean algebra. This field of mathematics is used in computers for decision making and doing arithmetic and logical operations on string of zeros and ones.

The mechanical er of computation was followed by the vacuum tubes, this was a revolution and led to the design of ENIAC (Enhances numeric integrator and calculator), it was made using around 17468 vacuum tubes. It was very huge in size and very unrelaible and had a very short life as in 1950 brought to halt caused by a short circuit.

An alternate to vacuum tubes were the transistor invented in 1947 by three physicists working at Bell Telephone Laboratories (Bell Labs). John Bardeen(1908–1991), Walter Brattain (1902–1987), and William Shockley (1910–1989). They thoght that transistors made from semiconductor material like germanium and silicon could be better alternatives to vacuum tubes. Robert Noyce (1927–1990) and research chemist Gordon Moore after sepation from William Shockley formed their own compny Fairchild and started working why not to make common circuitary using number of transistors. This idea led to the invention of Monolithic Integrated Circuit in 1960. Soon the scientist started working on large and very large scale integration. With the ide of integration in mind Robert Noyce and Gordon Moore established their own company integrated electronics and became popular by INTEL. They came up with the idea of a system on a chip and this was the time that the microprocessor came into existance. The microprocessor also have no a long history so they can be better described as generation of microprocessors.

Generation of Microprocessors

The electronic industry at this time was fully ripe. The pace with which work on microprocessor was going on was very high. Lot of compnies jumped in the race of manufacturing the single chip microprocessors. The number of microprocessors can better be described in various somewhat ovelapping periods called generations and is described below.

First Generation of Microprocssor (1971 – 73)

Intel came up with its first 4-bit microprocessor called Intel-4004 in 1971. Soon Intel came up with an enhanced version of 4004 called Intel 4040. Other compnies such as Rockwell international introduced PPS-4, Toshiba also introduced its 4-bit microprocessor T3472. This era was dominated by 4-bit processors though 8-bit microprocessors such a microprocessor based on PMOS technolgy as Intel 8008 in 1972 and Intel 8080 in 1973 using NMOS technology

Second Generation Microprocessors (1974-78): This era was dominated by 8-bit microprocessors such as Intel 8085 in 1975. This processor was an enhanced version of Intel 8080 required only a single power source of 5V and operated at 2MHz clock frequency. This is a very popular series of microprocessors used in universities for laboratory works.Some other popular microprocessors in this era were Motorola MC6800, MC6806, Zilog Z-80 and Z-800; MOS technology 6500 and National semiconductor introduced NSC-800.

Third Generation Microprocessors (1979-81): The third generation was dominated by 16-bit microprocessors. Intel introduced 8086 as its first 16-bit microprocessor. Other processors were Intel 8088 which had external 8-bit data bus but an internal 16-bit datapath. Other 16-bit mirprocessor by Intel were 80186 and 80286. Motorolla introduced 68000,68010; Zilog intrduced its Z8000; Texa’s instruments introduced its 16-bit TMS-9900. Intersil and Toshibas introduced their 12-bit microprocessors. Intel 8088 was very popular and was used in cheap personnel computers.

Fourth Generation Microprocessrs (1982-95):

This ear was of the 32-bit microprocessors. Intel introuced its 32-bit processors as Intel 386, Intel-486. They were videly used in desktop computers. Motorola 68020, 68030 and 768040 were also popular in desctop computers.

Fifth and beyond generation microprocessor(1996 to present):

This is dominated 64-bit microprocessor era and less dominant 32-bit processors which were popular during the transition phase. Though literature als define higher generation as 6th, 7th, 8th generation bu we restrict our discussion t fifth and higher generation covering all processors built till date. Some examples being the microprocessors of this era are SUN’s ULTRSPARK, PwerPC 620, MIPS, R4000, Intel PA8000, Intel i860 and the latest core series processors as i3, i5, i7 microprocessors.

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