Published by: Nuru
Published date: 18 Jun 2021
A microprocessor is a computer processor that incorporates the functions of a central processing unit on a single integrated circuit (IC), or sometimes up to 8 integrated circuits. Microprocessors contain both combination logic and sequential digital logic. Microprocessors operate on numbers and symbols represented in the binary number system. The microprocessor operates in binary 0 and 1 known as bits are represented in terms of electrical voltages in the machine that means 0 represents low voltage level and 1 represents high voltage level.
A microprocessor is a general-purpose entity. Several specialized processing devices have followed:
Terms used:
We can categorize the microprocessor according to the generations or according to the size of the microprocessor:
1.First Generation (4 - bit Microprocessors)
The first generation microprocessors were introduced in the year 1971-1972 by Intel Corporation. It was named Intel 4004 since it was a 4-bit processor. It was a processor on a single chip. It could perform simple arithmetic and logical operations such as addition, subtraction, Boolean OR and Boolean AND. I had a control unit capable of performing control functions like fetching an instruction from storage memory, decoding it, and then generating control pulses to execute it.
2.Second Generation (8 - bit Microprocessor)
The second generation microprocessor were introduced in 1973 again by Intel. It was a first 8 - bit microprocessor which could perform arithmetic and logic operations on 8-bit words. It was Intel 8008, and another improved version was Intel 8088.
3. Third Generation (16 - bit Microprocessor)
The third generation microprocessor, introduced in 1978 were represented by Intel's 8086, Zilog Z800 and 80286, which were 16 - bit processors with a performance like minicomputers.
4.Fourth Generation (32 - bit Microprocessor)
Several different companies introduced the 32-bit microprocessor, but the most popular one is the Intel 80386.
5.Fifth Generation (64 - bit Microprocessor)
From 1995 to now we are in the fifth generation. After 80856, Intel came out with a new processor namely Pentium processor followed by Pentium Pro CPU, which allows multiple CPUs in a single system to achieve multiprocessing. Other improved 64-bit processors are Celeron, Dual, Quad, Octa Core processors.
Low Cost - Due to integrated circuit technology microprocessors are available at very low cost. It will reduce the cost of a computer system.
High Speed - Due to the technology involved in it, the microprocessor can work at very high speed. It can execute millions of instructions per second.
Small Size - A microprocessor is fabricated in a very less footprint due to very large scale and ultra large scale integration technology. Because of this, the size of the computer system is reduced.
Versatile - The same chip can be used for several applications, therefore, microprocessors are versatile.
Low Power Consumption - Microprocessors are using metal oxide semiconductor technology, which consumes less power.
Less Heat Generation - Microprocessors uses semiconductor technology which will not emit much heat as compared to vacuum tube devices.
Reliable - Since microprocessors use semiconductor technology, therefore, the failure rate is very less. Hence it is very reliable.
Portable - Due to the small size and low power consumption microprocessors are portable.
8085 Microprocessor
The 8085 microprocessor is designed by Intel in the year of 1977 with the help of NMOS technology. The 8085 microprocessor is pronounced as an eighty-eighty-five microprocessor and the configurations of this microprocessor are the 8-bit data bus, 16-bit address bus, it can address up to 64kb, 16-bit programmer counter & stack pointer, the six-bit registers are arranged in the pair of BC, DE, & HL. The 8085 microprocessor requires a 5-volt power supply.
8086 Microprocessor
This microprocessor is also designed by the Intel and the 8086 microprocessor has a 16-bit microprocessor with 20 address lines and 16 data lines with storage of 1MB. The 8086 microprocessor consists of a powerful instruction set, which gives the operations like multiplications, divisions easily. The 8086 microprocessor has two modes of operations, which are maximum mode and minimum mode of operations. The maximum mode of operation is used for the system having multiple processors. The minimum mode of operation is used for the system having the single processor. The features of this microprocessor are explained below.
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8085 Microprocessor |
8086 Microprocessor |
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RISC and CISC Processors
RISC stands for Reduced Instruction Set Computer and CISC stands for Complex Instruction Set Computer. There are two approaches of the design of the control unit of a microprocessor i.e.-Hardware approach and
Software approach.
RISC Processors:- To execute an instruction, a number of steps are required. By the control unit of the processor, a number of control signals are generated for each step. To execute each instruction, if there is a separate electronic circuitry in the control unit, which produces all the necessary signals, this approach of the design of the control section of the processor is called RISC design. It is hardware approach. It is also called hard-wired approach.
CISC Processors:- If the control unit contains a number of micro electronic circuitry to generate a set of control signals and each micro circuitry is activated by a microcode, this design approach is called CISC design. This is a software approach of designing a control unit of the processor.
| S.No. | RISC | CISC |
|---|---|---|
| 1. | Simple instruction set | Complex instruction set |
| 2. | Consists of Large number of registers. | Less number of registers |
| 3. | Larger Program | Smaller program |
| 4. | Simple processor circuitry (small number of transistors) | Complex processor circuitry (more number of transistors) |
| 5. | More RAM usage | Little Ram usage |
| 6. | Simple addressing modes | Variety of addressing modes |
| 7. | Fixed length instructions | Variable length instructions |
| 8. | Fixed number of clock cycles for executing one instruction | Variable number of clock cycles for each instructions |