The microprocessor is the brain of a computer. It is also referred to as a processor or CPU; its main function is to execute the processes that come for execution. Generally, a processor fixes inside the CPU (Central Processing Unit) as a core component on the motherboard of the CPU. It”s composed of an arithmetic logic unit (ALU), a control unit, and registers. Microprocessors were first introduced in the early 1970s. 4004 was the first general-purpose microprocessor designed by Intel for personal computers.

Some common terminologies linked with microprocessors is as follows −

• Instruction Set Architecture (ISA) − A microprocessor executes a set of instructions. The basic computations include arithmetic, logic operations, data movement, and control transfer.
• Registers − Registers are the smaller units to store data while it is being processed. Registers are high-speed storage in the CPU. Some common examples are accumulators, programme counters, and general-purpose registers.
• Clock Speed − The rate at which a microprocessor executes instructions is measured in cycles per second (Hertz). Higher clock speeds often lead to faster processing.
• Cores − A modern microprocessor includes multiple processing cores, which allows them to execute multiple instructions simultaneously and enhance overall speed.
• Pipelines − It’s a method to increase instruction throughput by dividing instruction execution into multiple stages.
• Cache Memory − High-speed memory fixes close to the CPU to store frequently accessed data and instructions. It minimises access time and enhances system performance.
• Memory Management − System memory management is a process of allocating memory to processes, moving data between memory and storage, and ensuring that memory resources are used efficiently.
• Interrupts − Signals from external devices that cause the CPU to halt its current activities and manage interrupt requests.
• Bus Architecture − It facilitates communication between components like CPU, memory, and peripherals using buses to transfer data.

Microprocessor Components

Microprocessors serve as the central processing unit (CPU) in computers and other electronic devices. A microprocessor consists of different key components; every component dedicatedly works for the processor. Some key components of the microprocessor are as follows −

• CPU
• Bus
• Memory

CPU

CPU is fabricated as a very large-scale integrated circuit (VLSI) and has these parts −

• Instruction register − It holds the instruction to be executed.
• Decoder − It decodes (converts to machine-level language) the instruction and sends it to the ALU (Arithmetic Logic Unit).
• ALU − It’s dedicatedly designed to perform arithmetic operations (like add, subtract, multiply, divide, and compare numbers), logical operations (like AND, OR, and NOT), memory, register and program sequencing operations.
• Control Unit (CU) − A control unit supervises instruction execution for smooth execution; it coordinates the processor”s actions with other units. It accesses instructions from memory, decodes them, and controls the flow of data within the processor.
• Register − these are very small, high-speed storage locations used to hold data temporarily during processing. Some most widely and commonly used registers in processors are instruction register (IR), program counter (PC), memory address register (MAR), memory data register (MDR), and general-purpose registers like accumulator, and index registers. Registers hold intermediate results obtained from processing.

Bus

Buses are the connection lines which are designed specifically to do the data transfer between multiple components of the system. Hence, it is used for the data communication. Buses carry actual data being processed by the CPU or transferred between system components like CPU and memory. It”s like the lanes on the highway where the vehicles move.

Data buses are an essential part of computer architecture that influence the speed and efficiency of data transfer within a system. They are available in a variety of sorts and configurations, including address buses, control buses, and data buses, with each serving a unique purpose in aiding system communication.

There are three types of buses in a microprocessor −

• Data Bus − Lines that carry data to and from memory are called data buses. It is a bidirectional bus with a width equal to the word length of the microprocessor.

  Data buses consist of parallel wires/lines that carry data in binary form like 0s and 1s. The width of the data bus controls how much data may be carried simultaneously. For example, a 32-bit data bus can transfer 32 bits of data in parallel, whereas a 64-bit data bus can transfer 64 bits at once.

• Address Bus − It is a unidirectional responsible for carrying the address of a memory location or I/O port from CPU to memory or I/O port. In addition to the data bus, the address bus is an important component of a computer”s architecture.

  A data bus transfers actual data between components, whereas the address bus transports information about where the data should go or originate from.

• Control Bus − Lines that carry control signals like clock signals, interrupt signals or ready signals are called control buses. They are bidirectional. These signals make sure that operations are carried out in a proper sequence and at the right time. For example – a signal that indicates to a device to interrupt its process is called an interrupt signal.

Memory

Microprocessor has two types of memory.

• RAM − Random Access Memory is a volatile memory; the data or information which is stored in RAM gets erased when power is switched off. Hence, it”s a temporary memory which stores data till a program is under execution; once execution is over all the related data get erased or when power is switched off.
• ROM − Read Only Memory is non-volatile memory whose data remains intact even after power is switched off. Microprocessor can read from it at any time; as its name implies the data of ROM can be read only, we cannot write or store data in ROM. write to it. Therefore; it is pre-programmed with most essential data like the booting sequence by the manufacturer.

Characteristics of Microprocessors

Microprocessors are multipurpose devices that can be designed for generic or specialized functions. The microprocessors of laptops and smartphones are general purpose whereas ones designed for graphical processing or machine vision are specialized ones. Some characteristics are common to all microprocessors.

These are the most important defining characteristics of a microprocessor −

• Clock speed
• Word size
• Instruction set

Clock speed

Every microprocessor has an internal clock that regulates the speed at which it executes instructions and also synchronizes it with other components. The speed at which the microprocessor executes instructions is called clock speed.

Clock speeds are measured in MHz or GHz where 1 MHz means 1 million cycles per second whereas 1 GHz equals 1 billion cycles per second. Here cycle refers to a single electric signal cycle.

Currently, microprocessors have clock speeds in the range of 3 GHz, which is the maximum that current technology can attain. Speeds more than this generate enough heat to damage the chip itself. To overcome this, manufacturers are using multiple processors working in parallel on a chip.

Word Size

The number of bits that can be processed by a processor in a single instruction is called its word size. Word size determines the amount of RAM that can be accessed in one go and the total number of pins on the microprocessor. The total number of input and output pins in turn determines the architecture of the microprocessor. The first commercial microprocessor Intel 4004 was a 4-bit processor. It had 4 input pins and 4 output pins. Number of output pins is always equal to the number of input pins. Currently, most microprocessors use 32-bit or 64-bit architecture.

Instruction Set

A command given to a digital machine to operate on a piece of data is called an instruction. A basic set of machine-level instructions that a microprocessor is designed to execute is called its instruction set. These instructions do carry out these types of operations −

• Data transfer
• Arithmetic operations
• Logical operations
• Control flow
• Input/output and machine control