1. © 2009 Prentice-Hall, Inc. 1

2. 2 Technology in Action Chapter 9 Behind the Scenes: A Closer Look at System Hardware

3. © 2009 Prentice-Hall, Inc. 3 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

4. © 2009 Prentice-Hall, Inc. 4 Binary Language Computers work in binary languageComputers work in binary language Consists of two numbers: 0 and 1Consists of two numbers: 0 and 1 Everything a computer does is broken down into a series of 0s and 1sEverything a computer does is broken down into a series of 0s and 1s Switches: Devices inside the computer that can be flipped between these two states: 1 or 0, on or offSwitches: Devices inside the computer that can be flipped between these two states: 1 or 0, on or off

5. © 2009 Prentice-Hall, Inc. 5 Switches Nonmechanical devices in computers that open and close circuitsNonmechanical devices in computers that open and close circuits Types of electrical switches:Types of electrical switches: –Vacuum tubes –Transistors: SemiconductorsSemiconductors –Integrated circuits Vacuum Tube Transistors Integrated Circuits

6. © 2009 Prentice-Hall, Inc. 6 The on/off state of a switch represents one bit of dataThe on/off state of a switch represents one bit of data Bit (binary digit)Bit (binary digit) –On = 1 –Off = 0 OFF 0 Switches Representing Data ON 1 01 OR = 1 bit

7. © 2009 Prentice-Hall, Inc. 7 The Binary Number System Describes a number as powers of 2Describes a number as powers of 2 Also referred to as base 2 numbering systemAlso referred to as base 2 numbering system Used to represent every piece of data stored in a computer: all of the numbers, letters, and instructionsUsed to represent every piece of data stored in a computer: all of the numbers, letters, and instructions

8. © 2009 Prentice-Hall, Inc. 8 The Binary Number System Number systems are organized ways to represent numbersNumber systems are organized ways to represent numbers Each number in one system has a corresponding number in another.Each number in one system has a corresponding number in another. 01011001 = 89 Binary Base 10 128 2x64 64 2x32 32 2x16 16 2x8 8 2x4 4 2x2 2 2x1 1 Binary 01011001 Base 10 0 +64 +0 +16 +8 +0 + 1 = 89

9. © 2009 Prentice-Hall, Inc. 9 Representing Letters and Symbols American Standard Code for Information Interchange (ASCII) –8 bits = 1 byte = alphanumeric character or symbol –256 different combinations Unicode –16 bits equal 1 byte –65,000 different combinations, used for all languages

10. © 2009 Prentice-Hall, Inc. 10 ASCII Chart

11. © 2009 Prentice-Hall, Inc. 11 The CPU: Processing Digital Information The CPU is the brains of the computerThe CPU is the brains of the computer Different types of CPUsDifferent types of CPUs –Intel and AMD chips: Used in most Windows-based PCs –Apple systems use different CPU design Differentiating CPUsDifferentiating CPUs –Processing power –Clock speed and cache

12. © 2009 Prentice-Hall, Inc. 12 Processors on the Market

13. © 2009 Prentice-Hall, Inc. 13 The CPU Machine Cycle FetchFetch –The program’s binary code is “fetched” from its temporary location in RAM and moved to the CPU DecodeDecode –The program’s binary code is decoded into commands that the CPU understands ExecuteExecute –The ALU performs the calculations StoreStore –The results are stored in the registers

14. © 2009 Prentice-Hall, Inc. 14 The 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 Clock speedClock speed –Number of pulses per second –Measured in hertz (Hz)

15. © 2009 Prentice-Hall, Inc. 15 The Control Unit Manages the switches inside the CPUManages the switches inside the CPU Is programmed by CPU designers to remember the sequence of processing stages for that CPUIs programmed by CPU designers to remember the sequence of processing stages for that CPU Moves each switch to its correct setting (on or off)Moves each switch to its correct setting (on or off) Then performs the work of that stageThen performs the work of that stage

16. © 2009 Prentice-Hall, Inc. 16 The Arithmetic Logic Unit (ALU) Part of the CPU designed to perform mathematical operations (addition, subtraction, multiplication, division, etc.)Part of the CPU designed to perform mathematical operations (addition, subtraction, multiplication, division, etc.) Also performs logical OR, AND, and NOT operationsAlso performs logical OR, AND, and NOT operations Is fed data from the CPU registersIs fed data from the CPU registers –Word size: Number of bits a computer can work with at a time

17. © 2009 Prentice-Hall, Inc. 17 Cache Memory Small amount of memory located on the CPU chip or near itSmall amount of memory located on the CPU chip or near it Stores recent or frequently used instructions and dataStores recent or frequently used instructions and data Used for quick access by the CPUUsed for quick access by the CPU Different levels of cacheDifferent levels of cache

18. © 2009 Prentice-Hall, Inc. 18 RAM: The Next Level of Temporary Storage Volatile: When you turn off your computer, the data is erasedVolatile: When you turn off your computer, 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 transfer data more quickly

19. © 2009 Prentice-Hall, Inc. 19 Types of RAM: DRAM Cheapest and most basic type of RAMCheapest and most basic type of RAM Loses its electrical charge, needs to be refreshedLoses its electrical charge, needs to be refreshed Many types of DRAMMany types of DRAM –SDRAM: Synchronous DRAM –DDR SDRAM: Double data rate SDRAM

20. © 2009 Prentice-Hall, Inc. 20 Types of RAM: SRAM Static RAM (SRAM)Static RAM (SRAM) –Does not lose its electrical charge –Faster than DRAM –More expensive than DRAM –Used only in locations like cache memory

21. © 2009 Prentice-Hall, Inc. 21 BusBus –Electrical pathway used to move data between components –Local bus or front side bus (FSB): Connects the CPU with the memory –Expansion bus: Connects the CPU with peripheral devices Buses: The CPU’s Data Highway 01100010 01110011 01001000 00100111

22. © 2009 Prentice-Hall, Inc. 22 Bus Performance Bus clock speedBus clock speed –Rate of speed data moves from one location to another –Measured in MHz (millions of clock cycles per second) Bus widthBus width –The number of bits of data moved on a bus at any one time –Measured in bits 16 bits16 bits 32 bits32 bits

23. © 2009 Prentice-Hall, Inc. 23 Types of Expansion Buses ISA and EISAISA and EISA –Found on older computers –Connect mouse, modem, and sound card PCIPCI –Faster than ISA and EISA –Found on modern computers –Connects network, modem, and sound cards AGPAGP –Used for three-dimensional graphics –Connects the graphics card and memory

24. © 2009 Prentice-Hall, Inc. 24 Making Computers Faster Pipelining: The CPU processes more than one instruction at a timePipelining: The CPU processes more than one instruction at a time FetchDecodeExecuteStore FetchDecodeExecuteStore Instruction 1 Instruction 2 Nonpipelined CPU FetchDecodeExecuteStore FetchDecodeExecuteStore FetchDecodeExecuteStore FetchDecodeExecuteStore Instruction 1 Instruction 2 Instruction 3 Instruction 4 Pipelined CPU

25. © 2009 Prentice-Hall, Inc. 25 Making Computers Faster Specialized instructions for handlingSpecialized instructions for handling –Multimedia –Graphics

26. © 2009 Prentice-Hall, Inc. 26 Making Computers Faster Dual processingDual processing –Two CPUs on the same system –Each processor shares the workload Multi-core processingMulti-core processing HyperthreadingHyperthreading Parallel processingParallel processing –Network of computers –Each computer works on a portion of the problem simultaneously

27. © 2009 Prentice-Hall, Inc. 27 Chapter 9 Summary Questions What is a switch and how does it work in a computer?What is a switch and how does it work in a computer?

28. © 2009 Prentice-Hall, Inc. 28 Chapter 9 Summary Questions What is the binary number system, and what role does it play in computer system?What is the binary number system, and what role does it play in computer system?

29. © 2009 Prentice-Hall, Inc. 29 Chapter 9 Summary Questions What is inside the CPU, and how do these components operate?What is inside the CPU, and how do these components operate?

30. © 2009 Prentice-Hall, Inc. 30 Chapter 9 Summary Questions How does a CPU process data and instructions?How does a CPU process data and instructions?

31. © 2009 Prentice-Hall, Inc. 31 Chapter 9 Summary Questions What is cache memory?What is cache memory?

32. © 2009 Prentice-Hall, Inc. 32 Chapter 9 Summary Questions What types of RAM are there?What types of RAM are there?

33. © 2009 Prentice-Hall, Inc. 33 Chapter 9 Summary Questions What is a bus, and how does it function in a computer system?What is a bus, and how does it function in a computer system?

34. © 2009 Prentice-Hall, Inc. 34 Chapter 9 Summary Questions How do manufacturers make CPUs so that they run faster?How do manufacturers make CPUs so that they run faster?