1 Computer Literacy Chapter 9 Behind the Scenes: A Closer Look a System Hardware

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Computer LiteracyComputer Literacy

Chapter 9Chapter 9

Behind the Scenes: Behind the Scenes: A Closer Look a System HardwareA Closer Look a System Hardware

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Chapter Topics Chapter Topics

• Computer switchesComputer switches

• Binary number systemBinary number system

• Inside the CPUInside the CPU

• Cache memoryCache memory

• Types of RAMTypes of RAM

• Computer busesComputer buses

• Creating faster CPUsCreating faster CPUs

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Binary LanguageBinary Language

• Computers work in binary Computers work in binary languagelanguage

• Consists of two numbers: 0 and 1Consists of two numbers: 0 and 1• Everything a computer does is broken Everything a computer does is broken

down into a series of 0s and 1sdown into a series of 0s and 1s• Switches: Devices inside the Switches: Devices inside the

computer that can be flipped between computer that can be flipped between these two states: 1 or 0, on or offthese two states: 1 or 0, on or off

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SwitchesSwitches

• Non-mechanical devices in Non-mechanical devices in computers that open and close computers that open and close circuitscircuits

• Types of electronic switches:Types of electronic switches:– Vacuum tubesVacuum tubes– Transistors:Transistors:

• Semiconductors Semiconductors

– Integrated circuitsIntegrated circuits

Vacuum Tube

Transistors

Integrated Circuits

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• The on/off state of a switch represents one The on/off state of a switch represents one bit of databit of data

• Bit (binary digit)Bit (binary digit)– On = 1On = 1– Off = 0Off = 0

OFF

0

Switches Representing DataSwitches Representing Data

ON

1

01

OR = 1 bit

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The Binary Number SystemThe Binary Number System

• Describes a number as powers of 2Describes a number as powers of 2• Also referred to as base 2 numbering Also referred to as base 2 numbering

systemsystem• Used to represent Used to represent everyevery piece of data piece of data

stored in a computer: all of the numbers, stored in a computer: all of the numbers, letters, and instructionsletters, and instructions

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The Binary Number SystemThe Binary Number System

• Number systems are organized ways to represent Number systems are organized ways to represent numbersnumbers

• Each number in one system has a corresponding Each number in one system has a corresponding number in another.number in another.

01011001 = 89 Binary Base 10

1282x64

642x32

322x16

162x8

82x42x4

42x22x2

22x12x1

1

BinaryBinary 00 11 00 11 11 00 00 11

Base Base 1010

0 +0 + 64 +64 + 0 +0 + 16 +16 + 8 +8 + 0 +0 + 0 +0 + 1 =1 = 8989

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Representing Letters and SymbolsRepresenting Letters and Symbols

• American Standard American Standard Code for Information Code for Information Interchange (ASCII)Interchange (ASCII)– 8 bits = 1 byte = alphanumeric 8 bits = 1 byte = alphanumeric

character or symbolcharacter or symbol– 256 different combinations256 different combinations

• UnicodeUnicode– 16 bits equal 1 byte16 bits equal 1 byte– 65,000 different 65,000 different

combinations, used for all combinations, used for all languageslanguages

01100001 = a

01000001 = A

00100011 = #

01101101 = m

ASCII

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The CPU: The CPU: Processing Digital InformationProcessing Digital Information

• CPU is the brains of the CPU is the brains of the computercomputer

• Different types of CPUsDifferent types of CPUs– Intel and AMD chips: Used in Intel and AMD chips: Used in

most Windows-based PCsmost Windows-based PCs– Apple systems use different Apple systems use different

CPU designCPU design

• Differentiating CPUsDifferentiating CPUs– Processing powerProcessing power– Clock speed and cacheClock speed and cache

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Processors on the Market TodayProcessor Manufacturer # of

TransistorsTypical Clock Speed

Levels of Cache Storage

Notes

Athlon XP AMD 54.3 million 2.2 GHz 2 AMD processor that competes against the Pentium 4

Athlon 64 FX

AMD 106 million 2.6 GHz 2 64 bit processor for heavy computation and demanding video gaming needs

Centrino Intel 77 million 2.1 GHz 2 Designed specifically for mobile computer: has built-in wireless local network capabilities

Itanium 2 Intel 410 million 1.6 GHz 3 Seen in high-end server computers

Pentium 4Extreme Edition

Intel 169 million 3.7 GHz 3 The latest version of the Pentium chip. It uses dual cores and hyperthreading to process four tasks at once.

Pentium 4Processor

Intel 55 million 2.6 GHz 2 The M is for mobile. The chip uses less power so it can run longer on a battery charge.

PowerPC G4 Motorola 57 million 1.3 GHz 3 The only processor that, until 2006, powered the Apple line of computers. (iMac, PowerBooks, and so on)

PowerPC G5 IBM 58 million 2.5 GHz 2 Powerful 64-bit processor for heavy computational needs

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The CPU Machine CycleThe CPU Machine Cycle

• FetchFetch– The program’s binary code is “fetched” from its The program’s binary code is “fetched” from its

temporary location in RAM and moved to the CPUtemporary location in RAM and moved to the CPU

• DecodeDecode– The program’s binary code is decoded into commands The program’s binary code is decoded into commands

the CPU understands.the CPU understands.

• ExecuteExecute– The ALU performs the calculations.The ALU performs the calculations.

• StoreStore– The results are stored in the registersThe results are stored in the registers

“Inside the Chip” by Intel

Video Clip

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The System ClockThe System Clock

• Located on the motherboardLocated on the motherboard

• Controls the CPU’s processing cyclesControls the CPU’s processing cycles

• Clock cycleClock cycle– Pulse or tick Pulse or tick

• Clock speedClock speed– Number of pulses per secondNumber of pulses per second– Measured in hertz (Hz)Measured in hertz (Hz)

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The Control UnitThe Control Unit

• Manages the switches inside the CPUManages the switches inside the CPU• Is programmed by CPU designers to Is programmed by CPU designers to

remember the sequence of processing remember the sequence of processing stages for that CPU stages for that CPU

• Moves each switch to its correct setting Moves each switch to its correct setting (on or off) and then performs the work of (on or off) and then performs the work of that stagethat stage

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The Arithmetic Logic Unit (ALU)The Arithmetic Logic Unit (ALU)

• Part of the CPU designed to perform Part of the CPU designed to perform mathematical operations (addition, subtraction, mathematical operations (addition, subtraction, multiplication, division, etc.)multiplication, division, etc.)

• Also performs logical OR, AND, and NOT Also performs logical OR, AND, and NOT operationsoperations

• Is fed data from the CPU registersIs fed data from the CPU registers– Word size: Number of bits a computer can work with Word size: Number of bits a computer can work with

at a timeat a time

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Cache MemoryCache Memory

• Small amount of Small amount of memory located on the memory located on the CPU chip or near itCPU chip or near it

• Stores recent or Stores recent or frequently used frequently used instructions and datainstructions and data

• Used for quick access Used for quick access by the CPUby the CPU

• Different levels of cacheDifferent levels of cache

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RAM: The Next Level of RAM: The Next Level of Temporary StorageTemporary Storage

• Volatile: When you turn off your Volatile: When you turn off your computer, the data is erasedcomputer, the data is erased

• Several kinds of RAM existSeveral kinds of RAM exist• Each type of RAM has a different designEach type of RAM has a different design

– Some types work at much faster speeds Some types work at much faster speeds – Some transfer data more quicklySome transfer data more quickly

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Types of RAM: DRAMTypes of RAM: DRAM

• Dynamic RAM (DRAM)Dynamic RAM (DRAM)– Cheapest and most basic type of RAM Cheapest and most basic type of RAM – Loses its electrical chargeLoses its electrical charge– Needs to be refreshedNeeds to be refreshed– Many types of DRAMMany types of DRAM

• SDRAM: Synchronous DRAMSDRAM: Synchronous DRAM• DDR SDRAM: Double data rate SDRAMDDR SDRAM: Double data rate SDRAM

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Types of RAM: SRAMTypes of RAM: SRAM

• Static RAM (SRAM)Static RAM (SRAM)– Does not lose its electrical chargeDoes not lose its electrical charge– Faster than DRAMFaster than DRAM– More expensive than DRAMMore expensive than DRAM– Used only in locations like cache Used only in locations like cache

memorymemory

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• BusBus– Electrical pathway used to move data between Electrical pathway used to move data between

componentscomponents– Local bus: Connects the CPU with the memoryLocal bus: Connects the CPU with the memory– Expansion bus: Connects the CPU with peripheral Expansion bus: Connects the CPU with peripheral

devicesdevices

Buses: The CPU’s Data HighwayBuses: The CPU’s Data Highway

01100010

0111001101001000

00100111

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Bus PerformanceBus Performance

• Bus clock speedBus clock speed– Rate of speed data moves Rate of speed data moves

from one location to anotherfrom one location to another– Measured in Mhz (millions of Measured in Mhz (millions of

clock cycles per second)clock cycles per second)• Bus widthBus width

– The number of bits of data The number of bits of data moved on a bus at any one moved on a bus at any one timetime

– Measured in bitsMeasured in bits• 16 bits16 bits• 32 bits32 bits

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Types of Expansion BusesTypes of Expansion Buses• ISA and EISAISA and EISA

– Found on older computersFound on older computers– Connects mouse, modem, and sound cardConnects mouse, modem, and sound card

• PCIPCI– Faster than ISA and EISAFaster than ISA and EISA– Found on modern computersFound on modern computers– Connects network, modem, and sound cardsConnects network, modem, and sound cards

• AGPAGP– Used for three-dimensional graphicsUsed for three-dimensional graphics– Connects the graphics card and memoryConnects the graphics card and memory

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Moore’s LawMoore’s Law

• Number of transistors on a CPU will Number of transistors on a CPU will double every 18 monthsdouble every 18 months

• First chip had 29,000 transistorsFirst chip had 29,000 transistors

• Pentium chip 169,000,000 transistorsPentium chip 169,000,000 transistors

• Moore’s Law has been accurate for 25 Moore’s Law has been accurate for 25 yearsyears

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Making Computers FasterMaking Computers Faster• Pipelining: The CPU processes more than Pipelining: The CPU processes more than

one instruction at a timeone instruction at a time

Fetch Decode Execute

Store


Store

Instruction 1

Instruction 2

Non-pipelined CPU


Store


Store


Store


Store

Instruction 1

Instruction 2

Instruction 3

Instruction 4

Pipelined CPU

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Making Computers FasterMaking Computers Faster

• Dual processingDual processing– Two CPUs on the same Two CPUs on the same

systemsystem– Each processor shares Each processor shares

the workloadthe workload

• Parallel processingParallel processing– Network of computersNetwork of computers– Each computer works on Each computer works on

a portion of the problem a portion of the problem simultaneouslysimultaneously

Dual processors

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Chapter 9 Summary QuestionsChapter 9 Summary Questions

• What is a switch and how does it work in a What is a switch and how does it work in a computer?computer?

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• What is the binary number system and What is the binary number system and what role does it play in computer system?what role does it play in computer system?

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• What is inside the CPU and how do these What is inside the CPU and how do these components operate?components operate?

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• How does a CPU process data and How does a CPU process data and instructions?instructions?

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• What is cache memory?What is cache memory?

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• What types of RAM are there?What types of RAM are there?

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• What is a bus and how does it function in What is a bus and how does it function in a computer system?a computer system?

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• How do manufacturers make CPUs so that How do manufacturers make CPUs so that they run faster?they run faster?

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1 Computer Literacy Chapter 9 Behind the Scenes: A Closer Look a System Hardware