66 CHAPTER THE SYSTEM UNIT. © 2005 The McGraw-Hill Companies, Inc. All Rights Reserved. 6-2...

66CH

APT

ER

THE SYSTEM UNIT

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Competencies

Details about memoryMemory Classification BasesCache MemoryVirtual Memory

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Quiz03

Next Lecture – (Lecture #13)Contents:

Chapter 4 – The System UnitLecture Slides- #10 - #12

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Memory Classification Bases

Reading/ Writing CapabilityRead Only MemoryRead/ Write Memory

Data Access MechanismSequential Access MemoryRandom Access Memory

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… Memory Classification Bases

Volatility of Data No Data Loss without Electricity (Non-volatile Memory)Data loses without electricity (Volatile Memory)Data can be changed and be permanently saved once changed (CMOS Memory)

Speed of AccessCache Memory (Very high accessing speed)

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Memory

Holding area for data, instructions, and information Types of memory chips

RAM – holds programs and data

ROM – fixed start-up instructions

CMOS – flexible start-up instructions

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RAM

Random Access MemoryPrimary Memory of a computerData and Program needs to be loaded for processingAny memory location can be accessed randomlyVolatile storage Uses Cache support for increased efficiencyFlash RAM – Non-volatile/ portable

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ROM

Read-only memoryFirmwareCannot be changed by the userStart-up instructions, keyboard control capabilities

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CMOS

Complementary metal-oxide semiconductorFlexible and expandableStartup informationNon-volatileIts contents may be updated

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….The Memory (More Concepts)

Virtual MemoryA technique used to make huge programs run on small memory size computersA huge program is divided into many portionsEach portion could be adjusted inside the RAMProgram is then run by loading only the needed portion from hard diskOperating System (OS-win98) is the one who is taking care of this transparently.Effect: The program runs slowly

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… The Memory (More Concepts)

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Memory Capacity

UnitUnit CapacityCapacityMegabyte (MB) 1 billion bytes

Gigabyte (GB) 1 million bytes

Terabyte (TB) 1 trillion bytes