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Technology in Action Chapter 9 Behind the Scenes: A Closer Look at System Hardware Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 1 Binary Language • Computers work in binary language. • Consists of two numbers: 0 and 1 • Everything 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 off Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 2 Switches • Nonmechanical devices in computers that open and close circuits • Types of electrical switches Vacuum Tube – Vacuum tubes – Transistors • Solid state Semiconductors Transistors – Integrated circuits (very small transistors billions per square inch) Integrated Circuits Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 3 Switches Representing Data • The on/off state of a switch represents one bit of data. OFF ON • Bit (binary digit) – On = 1 – Off = 0 0 1 OR 1 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall = 1 bit 0 4 The Binary Number System • Describes a number as powers of 2 • Also referred to as base 2 numbering system • Used to represent every piece of data stored in a computer: all of the numbers, letters, and instructions Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 5 The Binary Number System • Number systems are organized ways to represent numbers. • Each number in one system has a corresponding number in another. Binary Base 10 128 2x64 64 2x32 32 2x16 16 2x8 8 2x4 4 2x2 2 2x1 1 0 1 0 1 1 0 0 1 0+ 0+ 0 + 64 + 0 + 16 + 8 + 1 = 89 01011001 = 89 Binary Base 10 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 6 The Binary Number System • Any whole number can be precisely represented (max 18,446,744,073,709,600,000) •Fractions may not be precise •Same problem as decimal numbers, for example: •What is 2/3 ? .6666666666→∞ •Solution: round to precision desired 7 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 or character – 65536 different combinations; used to define all alphabets Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 8 ASCII Chart Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 9 The CPU: Processing Digital Information • The brains of the computer • Different types of CPUs • Differentiating CPUs – Processing power – Clock speed and cache – Intel and AMD chips: Used in most Windows-based PCs and most newer Apple systems – Some older Apple systems use a different CPU design Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 10 Graphics Processing Unit (GPU) • Performs the same work as a CPU • Specialized to handle – 3D graphics – Image processing – Video processing • CPUs perform better with a GPU handling graphics computation. Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 11 The CPU Machine Cycle • Fetch – The next instruction is “fetched” from its location in RAM and moved to the CPU. • Decode – The CPU circuitry is prepared to execute the instruction. • Execute – The instruction is executed. “Inside the Chip” by Intel Video Clip • Store – The results are stored in memory or registers. Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 12 The System Clock • Located on the motherboard • Controls the CPU’s processing cycles • Clock cycle – Pulse or tick • Clock speed – Number of pulses per second – Measured in hertz--Hz, megahertz--MHz, gigahertz--GHz Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 13 The Future of RAM • Magnetoresistive Random Access Memory (MRAM) – Uses magnetic plates to store data • Nano Random Access Memory (NRAM) – Uses carbon nanotubes to store data • Something?? we don’t know about yet Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 14 The Control Unit The part of the CPU that: • Manages the switches inside the CPU • Is programmed by CPU designers to remember the sequence of processing stages for that CPU • Moves each switch to its correct setting (on or off) • Then performs the work of that stage Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 15 The Arithmetic Logic Unit (ALU) • The Part of the CPU designed to perform mathematical operations (addition, subtraction, multiplication, division, etc.) • Also performs logical OR, AND, and NOT operations • Is fed data from the CPU registers – Word size: Number of bits a computer can work with at a time (8, 16, 32, 64) Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 16 Cache Memory-- more is better • Small amount of very fast memory located on or near the CPU chip or both • Stores recent or frequently used instructions and data • Used for quick access by the CPU • Different levels of cache—L1 on chip, L2 off Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 17 RAM--main memory, holds the programs to be executed • Volatile: When you turn off your computer, the data is erased. • Several kinds of RAM exist. • Each type of RAM has a different design. – Some types work at much faster speeds. – Some transfer data more quickly. Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 18 Types of RAM: DRAM-dynamic ram • Most inexpensive and most basic type of RAM • Loses its electrical charge; needs to be refreshed • Many types of DRAM – SDRAM: Synchronous DRAM – DDR SDRAM: Double data rate of SDRAM – DDR2 SDRAM: Twice as fast as DDR SDRAM – Dual-Channel DDR2: Faster than DDR2 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 19 Types of RAM: SRAM • Static RAM (SRAM) – Does not lose its electrical charge – Faster than DRAM (on CPU chip) – More expensive than DRAM – Used only in locations like cache memory – Used in thumb drives and other pseudo-disks Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 20 Buses: The CPU’s Data Highway • Bus – 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 controllers – Bus speed improves with technology 01100010 01001000 01110011 00100111 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 21 Bus Performance • Bus clock speed – Rate of speed data moves from one location to another – Measured in MHz (millions of clock cycles per second) • Bus width – The number of bits of data moved on a bus at any one time – Measured in bits • 16 bits • 32 bits (PCI) • 64 bits (PCI) Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 22 Types of Expansion Buses • ISA and EISA – Found on older computers – Connect mouse, modem, and sound card • PCI and PCI-x – Faster than ISA and EISA – Found on modern computers – Connect network, modem, and sound cards • AGP (accelerated graphics port) – Used for three-dimensional graphics – Connects the graphics card and memory Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall 23 Making Computers Faster • Pipelining: The CPU processes more than one instruction at a time Nonpipelined CPU Instruction 1 Fetch Decode Execute Store Instruction 2 Fetch Decode Execute Store Pipelined CPU Instruction 1 Fetch Instruction 2 Decode Fetch Execute Decode Store Execute Store Fetch Decode Execute Store Instruction 4 Fetch Decode Execute Instruction 3 Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall Store 24 Making Computers Faster • Overclocking (can overheat and damage) • Dual processing – Two CPUs on the same system – Each processor shares the workload – Each could specialize—computing, communications • Multi-core processing—sharing of workload, like graphics, I/O • Hyperthreading—1 CPU doing 2 or more tasks at the same time, like math • Parallel processing (Supercomputers) – Network (or cluster) of computers – Each computer works on a portion of the problem simultaneously Copyright © 2010 Pearson Education, Inc. 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