Evolution and Components of Microprocessors: From Intel 4004 to Modern Processors, Schemes and Mind Maps of Electrical Engineering

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Introduction to Microprocessor

• The microprocessor is a multipurpose, clock driven, register based, digital-integrated circuit which accepts binary data as input, processes it according to instructions stored in its memory, and provides results as output.
• Microprocessor is a computer Central Processing Unit (CPU) on a single chip that contains millions of transistors connected by wires.
• A microprocessor is designed to perform arithmetic and logic operations that make use of small number-holding areas called registers.
• Typical microprocessor operations include adding, subtracting, comparing two numbers, and fetching numbers from one area to another.
• Microprocessor is capable of performing various computing functions and making decisions to change the sequence of program execution.

Generation of Microprocessors

2. INTEL 8008 (1972)

• 8-bit version of 4004
• 16 KB main memory
• 48 instructions
• PMOS technology
• Slow

Generation of Microprocessors

3. Intel 8080 (1973)

• 8-bit microprocessor
• 64 KB main memory
• 2 microseconds clock cycle time
• 500,000 instructions/sec
• 10X faster than 8008
• NMOS technology
• Drawback was that it needed three power supplies.

Generation of Microprocessors

5. INTEL 80186 (1982)

• 16-bit microprocessor-upgraded version of 8086
• 1 MB main memory
• Contained special hardware like programmable counters, interrupt controller etc.
• Never used in the PC
• But was ideal for systems that required a minimum of hardware.

Generation of Microprocessors

6. INTEL 80286 (1983)

• 16-bit high performance microprocessor with memory management & protection
• 16 MB main memory
• Few additional instructions to handle extra 15 MB
• Instruction execution time is as little as 250 ns
• Concentrates on the features needed to implement MULTITASKING

Components of Microprocessor

• The microprocessor can be divided into three segments as shown in the figure, Arithmetic/logic unit (ALU), register array, and control unit..

Components of Microprocessor

Arithmetic and logic unit (ALU)

• (^) It is the unit of microprocessor where various computing functions are performed on the data.
• (^) It performs arithmetic operations such as addition, subtraction, and logical operations such as OR,AND, and Exclusive-OR.
• (^) It is also known as the brain of the computer system.

Components of Microprocessor

Control unit

• (^) The control unit provides the necessary timing and control signals to all the operations in the microcomputer.
• (^) It controls and executes the flow of data between the microprocessor, memory and peripherals.
• (^) The control bus is bidirectional and assists the CPU in synchronizing control signals to internal devices and external components.
• (^) This signal permits the CPU to receive or

Classification of Microprocessors

Based on size of data bus:

• (^) 4-bit microprocessor (nibble)
• (^) 8-bit microprocessor (byte)
• (^) 16-bit microprocessor (word)
• (^) 32-bit microprocessor (long word) Bit: A bit is a single binary digit. Word: A word refers to the basic data size or bit size that can be processed by the arithmetic and logic unit of the processor. A 16-bit binary number is called a word in a 16-bit processor. Memory Word: The number of bits that can be stored in a register or memory element.

Classification of Microprocessors

Based on architecture:

• (^) Reduced Instruction Set Computer (RISC) processors – designed to perform a smaller number of types of computer instructions so that it can operate at a higher speed (millions of instructions per second, MIPS)
• (^) Complex Instruction Set Computer (CISC) processors – has the capacity to perform multi-step operations within one instruction set.

System bus

• (^) The network of wires or electronic pathways is called the 'Bus'.
• (^) A system bus is a single computer bus that connects the major components of a computer system.
• (^) It combines the functions of a data bus to carry information, an address bus to determine where it should be sent, and a control bus to determine its operation.
• (^) The technique was developed to reduce costs and improve modularity.

System bus

Address Bus

• (^) It is a group of wires or lines that are used to transfer the addresses of Memory or I/O devices.
• (^) It is unidirectional.
• (^) The width of the address bus corresponds to the maximum addressing capacity of the bus, or the largest address within memory that the bus can work with.
• (^) The addresses are transferred in binary format, with each line of the address bus carrying a single binary digit.
• (^) Therefore the maximum address capacity is equal to two to the power of the number of lines present (2^lines).

System bus

Data Bus

• (^) It is used to transfer data within Microprocessor and Memory/Input or Output devices.
• (^) It is bidirectional as Microprocessor requires to send or receive data.
• (^) Each wire is used for the transfer of signals corresponding to a single bit of binary data.
• (^) As such, a greater width allows greater amounts of data to be transferred at the same time.