What is a Microprocessor?

A digital Computer or Computer’s Central Processing Unit (CPU) built on a single Integrated Circuit (IC) is called a microprocessor. Since it is a programmable electronics chip of computing and decision making capabilities. The microprocessor contains numerous components like transistors, registers, and diodes that work together or programmable, multipurpose, clock -driven, register-based electronic device.   Any microprocessor based systems having limited number of resources are called microcomputers. It reads binary instructions from a storage device called memory, accepts binary data as input and processes data according to those instructions and provides results as output. Nowadays, microprocessor can be seen in almost all types of electronics devices such as mobile phones, printers, washing machines etc.

Block Diagram of a Microcomputer

Microprocessor Introduction

A microprocessor consists of an ALU, control unit and register array. ALU performs arithmetic and logical operations on the data received from an input device or memory. Control unit controls the instructions and flow of data within the computer. And, register array consists of registers identified by letters like B, C, D, E, H, L, and accumulator.

Evolution of Microprocessors

The category of microprocessor according to the generations or according to the size of the microprocessor:

First Generation (4 – bit Microprocessors configuration)

The first generation microprocessors were introduced in the year 1971 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. It had a control unit able to perform control functions and 4 bit data like fetching an instruction from storage memory, decoding it, and then generating control pulses to execute it. Intel introduced the enhanced version of 4004, the 4040. 4-bit Microprocessor.

• The INTEL 4004/4040 was invented in the year 1971 by Stanley Mazor & Ted Hoff.
• The clock speed of this microprocessor is 740 KHz.
• The number of transistors used in this microprocessor is 2,300 and instruction per second is 60K.
• The number of pins of this microprocessor is 16.

Second Generation (8 – bit Microprocessor configuration)

The second generation microprocessors 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.

• The 8008 processor was invented in the year 1972. The clock speed of this microprocessor is 500 KHz and instruction per second is 50K.
• The 8080 microprocessor was invented in the year 1974. The clock speed is 2 MHz. The number of transistors used is 60k and instruction per second is 10 times quicker as compared with 8008 processor.
• The 8085 microprocessor was invented in the year 1976. The clock speed is 3 MHz. The number of transistors used is 6,500 and instruction per second is 769230.
• The number of pins of this microprocessor is 40

Third Generation (16 – bit Microprocessor configuration)

The third generation microprocessors, introduced in 1978 were represented by Intel’s 8086, Zilog Z800 and 80286, which were 16 – bit processors with a performance like minicomputers.

• The 8086 microprocessor was invented in the year 1978. The clock speed is 4.77, 8 & 10 MHz. The number of transistors used is 29000 and instruction per second is 2.5 Million. The number of pins of this microprocessor is 40
• The 8088 microprocessor was invented in the year 1979 and instruction per second is 2.5 Million
• The microprocessors like 80186 or 80188 were invented in the year 1982. The clock speed is 6 MHz
• The 80286 microprocessor was invented in the year 1982. The clock speed is 8 MHz. The number of transistors used is 134000 and instruction per second is 4 Million.
• The number of pins of this microprocessor is 68 and 32-bit Microprocessor

Fourth Generation (32 – bit Microprocessors configuration)

Several different companies introduced the 32-bit microprocessors, but the most popular one is the Intel 80386.

• The Intel 80386 microprocessor was invented in the year 1986. The clock speed is 16 MHz to 33 MHz. The number of transistors used is 275000. The number of pins  is 132 14X14 PGA
• The Intel 80486 microprocessor was invented in the year1986. The clock speed is 16MHz to 100 MHz. The number of transistors used is 1.2 Million transistors and instruction per second is 8 KB of cache memory. The number of pins of this microprocessor is 168 17X17 PGA (Pin Grid Array)
• The PENTIUM microprocessor was invented in the year 1993. The clock speed is 66 MHz and instruction per second is Cache memory 8-bit for instructions 8- bit for data. The number of pins of this microprocessor is 237 PGA

Fifth Generation (64 – bit Microprocessors configuration)

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.

• The INTEL core 2 microprocessor was invented2006. The clock speed is 1.2 GHz to 3 GHz.
• The number of transistors used is 291 Million and instruction per second is 64 KB of L1 cache for each core 4 MB of L2 cache.
• The i3, i5, i7 microprocessors were invented in the years 2007, 2009, 2010 2. The clock speed is 2GHz to 3.3GHz, 2.4GHz to 3.6GHz & 2.93GHz to t 3.33GHz.

Other improved 64-bit processors are Celeron, Dual, Quad, Octa Core processors.

Important Intel Microprocessors abbreviation

PGA – Pin Grid Array

MMX – Multimedia Extensions

EPIC – Explicitly Parallel Instruction Computing

SIMD – Single Instruction Multiple Data

ALU – Arithmetic and Logic Unit

MMU – Memory Management Unit

FPU – Floating Point Unit

Microprocessor-based system

• Address Bus:
  It carries the address, which is a unique binary pattern used to identify  a memory location or an I/O port. For example, an eight bit address bus has eight lines and thus it can address 28 = 256 different locations. The locations in hexadecimal format can be written as 00H – FFH.
• Data Bus:

  The data bus is used to transfer data between memory and processor or between I/O device and processor. For example, an 8-bit processor will generally have an 8-bit data bus and a 16-bit processor will have 16-bit data bus.

• Control Bus:

  The control bus carry control signals, which consists of signals for selection of memory or I/O device from the given address, direction of data transfer and synchronization of data transfer in case of slow devices.

Basic Terms used in Microprocessor:

A list of some basic terms used in microprocessor:

• Instruction Set:

  The group of commands that the microprocessor can understand is called Instruction set. It is an interface between hardware and software.

• Bus :
  Set of conductors intended to transmit data, address or control information to different elements in a microprocessor. A microprocessor will have three types of buses, i.e., data bus, address bus, and control bus.
• IPC (Instructions Per Cycle) :
  It is a measure of how many instructions a CPU is capable of executing in a single clock.
• Clock Speed :
  It is the number of operations per second the processor can perform. It can be expressed in megahertz (MHz) or gigahertz (GHz). It is also called the Clock Rate.
• Bandwidth:
  The number of bits processed in a single instruction is called Bandwidth.
• Word Length:
  The number of bits the processor can process at a time is called the word length of the processor. 8-bit Microprocessor may process 8 -bit data at a time. The range of word length is from 4 bits to 64 bits depending upon the type of the microcomputer.
• Data Types:

  The microprocessor supports multiple data type formats like binary, ASCII, signed and unsigned numbers.

Working of Microprocessor

The microprocessor follows a sequence to execute the instruction: Fetch, Decode, and then Execute. Initially, the instructions are stored in the storage memory of the computer in sequential order. The microprocessor fetches those instructions from the stored area (memory), then decodes it and executes those instructions till STOP instruction is met. Then, it sends the result in binary form to the output port. Between these processes, the register stores the temporary data and ALU (Arithmetic and Logic Unit) performs the computing functions.

Features of Microprocessor

Low Cost:

Microprocessors are available at very low cost. It will reduce the cost of a computer system.

High Speed:

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 and will not emit much heat as compared to vacuum tube devices.

Reliable:

The failure rate is very less. Hence it is very reliable.

Portable :

small in size and low power consumption microprocessors are portable.