CPU(CENTRAL PROCESSING CENTRAL PROCESSING

UNIT)UNIT)

INTRODUCTION TO CPUINTRODUCTION TO CPU

The central processing unit (CPU) is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input and output operations of the system. It acts as the BRAIN OF COMPUTER.

HISTORY OF CPUHISTORY OF CPU

Early CPUs were custom-designed as a part Early CPUs were custom-designed as a part of a larger, sometimes one-of-a-kind, of a larger, sometimes one-of-a-kind, computer. However, this method of computer. However, this method of designing custom CPUs for a particular designing custom CPUs for a particular application has largely given way to the application has largely given way to the development of mass-produced processors development of mass-produced processors that are made for This standardization began that are made for This standardization began in the era of discrete transistor in the era of discrete transistor mainframes and minicomputers and has mainframes and minicomputers and has rapidly accelerated with the popularization of rapidly accelerated with the popularization of the integrated circuits (IC). the integrated circuits (IC).

The IC has allowed increasingly complex The IC has allowed increasingly complex CPUs to be designed and manufactured to CPUs to be designed and manufactured to tolerances on the order of nanometres. Both tolerances on the order of nanometres. Both the miniaturization and standardization of the miniaturization and standardization of CPUs have increased the presence of digital CPUs have increased the presence of digital devices in modern life far beyond the limited devices in modern life far beyond the limited application of dedicated computing application of dedicated computing machines. Modern microprocessors appear machines. Modern microprocessors appear in everything from in everything from automobiles to cellphones and children's automobiles to cellphones and children's toy. toy.

BLOCK DIAGRAM OF CPUBLOCK DIAGRAM OF CPU

COMPONENTS OF COMPONENTS OF CPUCPU

CONTROL UNIT(CU)CONTROL UNIT(CU)ARITHEMATIC ARITHEMATIC LOGIC UNIT (AU)LOGIC UNIT (AU)

A number of A number of RegistersRegisters

CONTROL UNIT (CU)CONTROL UNIT (CU)

Control Unit controls operations of other Control Unit controls operations of other parts of CPU as well as all parts of parts of CPU as well as all parts of computer by sending a control signal, computer by sending a control signal, e.g.e.g.

control sequence of instruction to be control sequence of instruction to be executedexecuted

control flow of data among all parts of control flow of data among all parts of computer computer

interpret instructionsinterpret instructionsregulate timing of procressorregulate timing of procressorsend control single to and recieve send control single to and recieve

control single from peripheral devicescontrol single from peripheral devices

ARITHMETIC AND ARITHMETIC AND LOGIC UNIT (ALU)LOGIC UNIT (ALU)

Arithmetic and Logic Unit Arithmetic and Logic Unit consists of a complicated set of consists of a complicated set of logic circuit and accumulator.logic circuit and accumulator.

It is mainly reponsible for :It is mainly reponsible for :CalculationCalculationLogical comparsion and decisionLogical comparsion and decision

REGISTERSREGISTERS Register is a sepecial memory used by the

CPU for temperarily storing data during execution of instruction

Intruction DecoderIt is a device which interprets the instruction to be executed.

Programer Counter (PC)It holds the address of next instruction to be executed.

Instruction Register (IR)It holds the instruction being executed.

Process Status RegisterIt holds “processor bit" about operation done by ALU.

Accumulator (ACC)It stores intermediate and final results of calulation. It's the main working area of ALU.

General Purpose RegisterIt can be used to store any temperary information during execution of instruction.

Memory Address Register (MAR)It holds address the data word to be accessed.

Memory Data Register (MDR) It holds the data word when it is transferred to and from the main memory.

Address DecoderIt interprets the address in the MAR and selects the appropriate cell in the main memory to be accessed.

How CPU works?How CPU works? The CPU is centrally located on the The CPU is centrally located on the

motherboard. Since the CPU carries out motherboard. Since the CPU carries out a large share of the work in the a large share of the work in the computer, data pass continually computer, data pass continually through it. The data come from the through it. The data come from the RAM and the units (keyboard, drives, RAM and the units (keyboard, drives, etc.). After processing, the data is sent etc.). After processing, the data is sent back to the RAM and the units. The CPU back to the RAM and the units. The CPU continually receives instructions to be continually receives instructions to be executed. Each instruction is a data executed. Each instruction is a data processing order. processing order.

MOTHERBOARDMOTHERBOARD

A motherboard is the physical A motherboard is the physical arrangement in a computer that contains arrangement in a computer that contains the computer's basic circuitry and the computer's basic circuitry and components. On the typical motherboard, components. On the typical motherboard, the circuitry is imprinted or affixed to the the circuitry is imprinted or affixed to the surface of a firm planar surface and surface of a firm planar surface and usually manufactured in a single step. usually manufactured in a single step. The computer components included in the The computer components included in the motherboard are: The microprocessor motherboard are: The microprocessor (Optionally) coprocessors Memory BIOS (Optionally) coprocessors Memory BIOS Expansion slots Interconnecting circuitry Expansion slots Interconnecting circuitry Additional components can be added to a Additional components can be added to a motherboard through its expansion slots. motherboard through its expansion slots.

MICROPROCESSOR

A microprocessor is a computer processor on a microchip. It's sometimes called a logic chip. It is the "engine" that goes into motion when you turn the computer on. 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.

These operations are the result of a set of instructions that are part of the microprocessor design. When the computer is turned on, the microprocessor is designed to get the first instruction from the basic input/output system (BIOS) that comes with the computer as part of its memory. After that, either the BIOS, or the operating system that BIOS loads into computer memory, or an application program is "driving" the microprocessor, giving it instructions to perform.

IMAGES OF MICROPROCESSORIMAGES OF MICROPROCESSOR

MICROCHIPMICROCHIP

A microchip (sometimes just called a "chip") is a unit of packaged computer circuitry (usually called an integrated circuit) that is manufactured from a material such as silicon at a very small scale. Microchips are made for program logic (logic or microprocessor chips) and for computer memory (memory or RAM chips).

IMAGES OF MICROCHIPIMAGES OF MICROCHIP

BIOSBIOS BIOS is an integral part of the computer and

comes with it when you bring it home. (In contrast, the operating system can either be preinstalled by the manufacturer or vendor or installed by the user.) BIOS is a program that is made accessible to the microprocessor on an eraseable programmable read-only memory (EPROM) chip. When you turn on the computer, the microprocessor passes control to the BIOS program, which is always located at the same place on EPROM.

When BIOS boots up (starts up) the computer, it first When BIOS boots up (starts up) the computer, it first determines whether all of the attachments are in determines whether all of the attachments are in place and operational and then it loads the operating place and operational and then it loads the operating system (or key parts of it) into the computer's system (or key parts of it) into the computer's random access memory RAM from the hard disk or random access memory RAM from the hard disk or diskette drive. With BIOS, the operating system and diskette drive. With BIOS, the operating system and its applications are freed from having to understand its applications are freed from having to understand exact details (such as hardware addresses) about exact details (such as hardware addresses) about the attached input/output devices. When device the attached input/output devices. When device details change, only the BIOS program needs to be details change, only the BIOS program needs to be changed. Sometimes this change can be made changed. Sometimes this change can be made during the system setup. In any case, neither the during the system setup. In any case, neither the operating system or any applications you use need operating system or any applications you use need to be changed.to be changed.