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The Central processing Unit

Machine Cycle

Information processing cycle

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The Central processing Unit•The CPU interprets instructions to the computer, performs the logical and arithmetic processing operations, and causes the input and output operations to occur. •consists of hundreds of thousands or millions of electronic circuits.•In today's PCs the CPU is contained in a single silicon chip called a microprocessor chip•It is considered the “brain” of the computer.•Also called the CPU as PROCESSOR & MICROPROCCESSOR

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Intel Pentium D AMD Athlion 64 Intel Pentium M

Pentium DPentium I-IVPentium MCeleronCore i7Core 2 Duo

AMDAthelon 64 X2Athelon 64Turion 64Sempron

Storage (Pimary/Secondary Memory)

Storage (Pimary/Secondary Memory)

Input OutputProcesorProcesor

HOW THESE COMPUTER WORKS?

Monitor,Printer

CPU must be connected to input device, output device and storage device to carry out the

activities

DataData InformationInformation

INFORMATION PROCESSING CYCLE

DataData InformationInformation

Processor / CPU

The Control processing unit (CPU) controls all activities within the system. For every instruction, the control unit repeats a set of four basic operations called the MACHINE CYCLE

A CPU consists of two subcomponents:-1. Control Unit (CU)2.Arithmetic Logic Unit (ALU).

Machine Cycle

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FETCHING

EXECUTING

STORING DECODING

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Machine Cycle

• 4 step in Machine Cycle :

• Step 1:Fetch – retrieve an instruction from memory

• Step 2:Decode – translate instruction in a form ALU can understand (command )

• Step 3:Execute – Carry out instruction• Step 4:Store – copy results to Memory

Processor

Control Unit

MEMORY

ALU

How it’s work ?

Step 1. Fetch Calls an instruction into memory. User want to calculate 2 +2

Step 2.

Decode Translate instruction into commands (to binary form)

Eg : 1110000

Step 4. Store Write result to memory

Step 3. Execute

Does the decoded instructionAdd 2+2

Four operations of the CPU comprise a machine cycle

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Control Unit

Control Unit’s main function in CPU to process data.

1.The Control Unit extracts instructions from memory and decodes and executes them.

2.Manages all resources of a computer

3.Manages a 4-step basic operation which is called a machine cycle or processing cycle.

The Arithmetic-Logic Unit and Control Unit

• An arithmetic logic unit (ALU) and control unit is one of the core components of all central processing units.

• Arithmetic operations: e.g., add, subtract, multiply, divide, square root, cosine, etc.

• Logical operations: e.g., compare two numbers to see which is greater, check whether a true/false statement is true, etc.

• Comparison operation : e.g:AND, OR, NOT, NAND, NOR, XOR and equacalence (=)

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Factors Affecting Processing Speed

• Clock rate of the CPU

• Computer word size

• Bus speed

• Main memory size

• Cache memory size

• instruction set complexity

• Number of processing units

Which computer should I buy?

Desktop

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