Overview of Computer Architecture & Organization

8/12/2019 Overview of Computer Architecture & Organization

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Module 1


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Architecture is those attributes visible to the

programmer

Instruction set, number of bits used for data

representation, I/O mechanisms, addressing

techniques.

e.g. Is there a multiply instruction?

Organization is how features are

implemented Control signals, interfaces, memory technology.

e.g. Is there a hardware multiply unit or is it

done by repeated addition?


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Computer: A device that accepts input,processes data, stores data, and produces output, allaccording to a series of stored instructions.

Hardware: Includes the electronic and

mechanical devices that process the data; refers tothe computer as well as peripheral devices.

Software:A computer program that tells thecomputer how to perform particular tasks.

Network: Two or more computers and otherdevices that are connected, for the purpose ofsharing data and programs.

Peripheral devices: Used to expand thecomputers input, output and storage capabilities.


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Input:Whatever is put into a computer system.

Data: Refers to the symbols that represent facts, objects,or ideas.

Information: The results of the computer storing data

as bits and bytes; the words, numbers, sounds, andgraphics.

Output: Consists of the processing results produced by acomputer.

Processing: Manipulation of the data in many ways.

Memory: Area of the computer that temporarily holdsdata waiting to be processed, stored, or output.Storage: Area of the computer that holds data on a

permanent basis when it is not immediately needed forprocessing.


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Two phases:

before VLSI 1945 1978

ENIAC IAS

IBM

PDP8

VLSI 1978 present day microprocessors !


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Program and data reside in the same memory

(stored program concepts John von

Neumann)

ALP was made used to write programs Vacuum tubes were used to implement the

functions (ALU & CU design)

Magnetic core and magnetic tape storage

devices are usedUsing electronic vacuum tubes, as the

switching components


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Transistor were used to design ALU & CU

HLL is used (FORTRAN)

To convert HLL to MLL compiler were used

Separate I/O processor were developed tooperate in parallel with CPU, thus improving

the performance

Invention of the transistor which was faster,

smaller and required considerably less powerto operate


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IC technology improve

Improved IC technology helped in designing low

cost, high speed processor and memory modules

Multiprogramming, pipelining concepts wereincorporated

DOS allowed efficient and coordinate operation

of computer system with multiple users

Cache and virtual memory concepts weredeveloped

More than one circuit on a single silicon chip

became available


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CPU Termed as microprocessor

INTEL, MOTOROLA, TEXAS,NATIONALsemiconductors started developingmicroprocessor

Workstations, microprocessor (PC) &Notebook computers were developed

Interconnection of different computer forbetter communication LAN,MAN,WAN

Computational speed increased by 1000times

Specialized processors like Digital SignalProcessor were also developed


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ECommerce, Ebanking, home office

ARM, AMD, INTEL, MOTOROLA

High speed processor GHz speed

Because of submicron IC technology lot ofadded features in small size


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Simply put, a computer is a sophisticatedelectronic calculating machinethat: Accepts input information,

Processes the information according to a list ofinternally stored instructions and

Produces the resulting output information.

Functions performed by a computerare: Accepting information to be processed as input.

Storing a list of instructions to process theinformation.

Processing the information according to the list ofinstructions.

Providing the results of the processing as output.

What are the functional units of a computer?


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I/O Processor

Input

Output Control

Arithmeticlogic unit

Memory

Input unit acceptsinformation:Human operators,Electromechanical devicesOther computers

Output unit sendsresults of processing:To a monitor display,

To a printer

Arithmetic and logic unit(ALU):Performs the desiredoperations on the inputinformation as determinedby instructions in the memory

Storesinformation:Instructions,Data Control unit coordinates

various actionsInput,OutputProcessing


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Instructions specify commands to: Transfer information within a computer (e.g., from memory to

ALU)

Transfer of information between the computer and I/O devices(e.g., from keyboard to computer, or computer to printer)

Perform arithmetic and logic operations (e.g., Add two numbers,

Perform a logical AND).

A sequence of instructions to perform a task is

called a program, which is stored in the memory.

Processor fetches instructions that make up aprogram from the memory and performs the

operations stated in those instructions.

What do the instructions operate upon?


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Data are the operands upon which

instructions operate.

Data could be:

Numbers, Encoded characters.

Data, in a broad sense means any digital

information.

Computers use data that is encoded as astring of binary digits called bits.


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Input Unit

Processor

Memory

ComputerReal world

Keyboard

Audio input

Binary information must be presented to a computer in a specific format. This

task is performed by the input unit:

- Interfaces with input devices.

- Accepts binary information from the input devices.

- Presents this binary information in a format expected by the computer.

- Transfers this information to the memory or processor.


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Memory unit stores instructions and data. Recall, data is represented as a series of bits.

To store data, memory unit thus stores bits.

Processor reads instructions and reads/writes

data from/to the memory during the executionof a program. In theory, instructions and data could be fetched one bit at a time.

In practice, a group of bits is fetched at a time.

Group of bits stored or retrieved at a time is termed as word

Number of bits in a word is termed as the word length of acomputer.

In order to read/write to and from memory, aprocessor should know where to look: Address is associated with each word location.


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Processor reads/writes to/from memory based onthe memory address: Access any word location in a short and fixed amount of timebased on

the address.

Random Access Memory (RAM) provides fixed access timeindependent

of the locationof the word. Access time is known as Memory Access Time.

Memory and processor have to communicate witheach other in order to read/write information. In order to reduce communication time, a small amount of RAM

(known as Cache) is tightly coupled with the processor.

Modern computers have three to four levels of RAM units with differentspeeds and sizes:

Fastest, smallest known as Cache

Slowest, largest known as Main memory.


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Primary storage of the computer consists of RAMunits. Fastest, smallest unit is Cache.

Slowest, largest unit is Main Memory.

Primary storage is insufficient to store large

amounts of data and programs. Primary storage can be added, but it is expensive.

Store large amounts of data on secondarystorage devices: Magnetic disks and tapes,

Optical disks (CD-ROMS). Access to the data stored in secondary storage in slower, but take

advantage of the fact that some information may be accessedinfrequently.

Cost of a memory unit depends on its accesstime, lesser access time implies higher cost.


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Operations are executed in the Arithmetic andLogic Unit (ALU). Arithmetic operations such as addition, subtraction.

Logic operations such as comparison of numbers.

In order to execute an instruction, operandsneed to be brought into the ALU from thememory. Operands are stored in general purpose registersavailable in the

ALU.

Access times of general purpose registers are faster than the

cache.

Results of the operations are stored back in thememory or retained in the processor forimmediate use.


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Computers represent information in a specific binary form. Output units:

- Interface with output devices.

- Accept processed results provided by the computer in specific binary form.

- Convert the information in binary form to a form understood by an

output device.

Output Unit

Processor

Memory

Computer Real world

Printer

Graphics display

Speakers


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Operation of a computer can be summarizedas: Accepts information from the input units (Input unit).

Stores the information (Memory).

Processes the information (ALU).

Provides processed results through the output units (Output unit).

Operations of Input unit, Memory, ALU and

Output unit are coordinated by Control unit.

Instructions control what operationstake

place (e.g. data transfer, processing). Control unit generates timing signals which

determines when a particular operationtakes

place.


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For a computer to achieve its operation, the functional units need tocommunicate with each other.

In order to communicate, they need to be connected.

MemoryInput Output Processor

Functional units may be connected by a group of parallel wires.

The group of parallel wires is called a bus.

Each wire in a bus can transfer one bit of information.

The number of parallel wires in a bus is equal to the word length of

a computer

Bus


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MAR

PC

IR

MDR

Control

ALU

R0

R1

Rn-1

.

.

.

n general purpose

registers

Memory

Processor


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Overview of Computer Architecture & Organization

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