Microprocessor

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.

Special-purpose designs

A microprocessor is a general-purpose entity. Several specialized processing devices have followed:

A digital signal processor(DSP) is specialized for signal processing.
Graphics processing units(GPUs) are processors designed primarily for real time rendering of images.
Other specialized units exist for video processing and machine vision. (See: Hardware acceleration.)
Micro-controllers integrate a microprocessor with peripheral devices in embedded systems.
Systems on chip (SoCs) often integrate one or more microprocessor or micro-controller cores.

Terms used:

CPU: – Central processing unit which consists of ALU and control unit.
Microprocessor: – Single chip containing all units of CPU.
Microcomputer: – Computer having microprocessor as CPU.
Micro-controller: single chip consisting of MPU, memory, I/O and interfacing circuits.
MPU: – Micro processing unit – complete processing unit with the necessary control signals.

Evolution of Microprocessors

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.

Features of Microprocessor

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.

Types of Microprocessor

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.

8085 Microprocessor	8086 Microprocessor
It is an 8-bit microprocessor	This is a 16-bit microprocessor
It has 16-bit address bus	8086 has 20-bit address bus
In this, the memory can access up to 64kb	Where in the process the memory is up to 1 MB
The 8085 processor does not consist of pipeline architecture	While in the 8086 processors consist of pipeline architecture
In this processor, the I/O address is 2⁸ = 256 I/O’s	In the 8086 processors, the I/O address is about 2¹⁶ = 65536 I/O’s
The cost of this processor is low	The cost of this processor is high

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.

Difference between RISC and CISC

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

Evolution, Features and Types of Microprocessors || Introduction of Microprocessor || Bcis Notes