TECHNOLOGY IN ACTION

Technology in Focus Under the Hood

Switches and Number Systems Electrical Switches Computer system Enormous collection of on/off switches Combined to perform addition, subtraction, and move data around Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 3

Switches and Number Systems Electrical Switches Computers only understand two states Binary language consists of two numbers: 1 or 0 Electrical switches can be switched between 1 and 0 signifying ON and OFF Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 4 Lock Computers contain a huge collection of electrical switches

Switches and Number Systems Vacuum Tubes Used as switches Earliest generation computers Allow or block flow of electrical current Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 5 Problems with vacuum tube switches Take up a large amount of space Produce heat and burn out frequently

Switches and Number Systems Transistors Electrical switches built of layers of materials called semiconductors Semiconductors can be controlled to conduct or insulate Made from silicon Smaller and faster than vacuum tubes Produce less heat, can be switched quickly, and are less expensive Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 6

Switches and Number Systems Transistors This silicon wafer has the transistor circuitry for hundreds of devices etched on it Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 7

Switches and Number Systems Integrated Circuits Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 8 Tiny regions of semiconductor material Support a huge number of transistors No more than ¼ inch in size Can fit billions of transistors CPUs are microprocessor chips

Switches and Number Systems Number Systems Base-10 number system Number system is an organized plan for representing a number Decimal notation Base 10 uses 10 digits (0–9) Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 9

Switches and Number Systems Number Systems Base-2 or binary uses two digits (0 and 1) Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 10

Switches and Number Systems Number Systems Hexadecimal notation Used to avoid working with long strings of 1s and 0s Base-16 uses 16 digits (0–9 and A–F) A = 10, B = 11, etc. Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 11

Switches and Number Systems Number Systems Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 12 American Standard Code for Information Interchange (ASCII) represents each letter or character as 8-bit binary code Each binary digit is a bit 8 binary digits (or bits) create one byte

Switches and Number Systems Number Systems Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 13 Unicode ASCII can only assign 256 unique codes Not sufficient for all languages Unicode uses 16 bits

Switches and Number Systems Number Systems IEEE established floating-point standard Describes how fractional parts should be represented in binary Uses a 32-bit system First digit indicates whether a number is positive or negative Next 8 bits store magnitude Remaining 23 bits store value of number Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 14

How the CPU Works The Machine Cycle Machine cycle refers to series of general steps CPU performs 1.Fetch 2.Decode 3.Execute 4.Store Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 15

How the CPU Works The Control Unit and the System Clock Manages switches inside CPU Remembers: Sequence of processing stages How switches are set for each stage With each beat of the system clock Control unit moves each switch to correct on/off setting Performs the work of that stage Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 16

How the CPU Works The Control Unit and the System Clock Moves CPU from one stage to the next Acts as a metronome, keeping steady beat or tick Ticks, known as the clock cycle, set the pace Pace, known as clock speed, is measured in hertz Today’s speed is measured in gigahertz, 1 billion clock ticks per second Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 17

How the CPU Works Machine Cycle Stages The fetch stage Data and program instructions stored in various areas of the system Program or data is moved to RAM from the hard drive As instructions are needed, they are moved from RAM into registers Storage areas located on CPU Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 18

How the CPU Works Machine Cycle Stages The decode stage CPU’s control unit decodes program’s instructions into commands Instruction set Commands CPU can execute Written in assembly language Assembly language translated into binary code Machine language—long strings of binary code Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 19

How the CPU Works Machine Cycle Stages The execute stage Arithmetic logic unit (ALU) Mathematical operations Test comparisons of values (, =) Logical OR, AND, and NOT operations Word size is number of bits worked with at a time Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 20

How the CPU Works Machine Cycle Stages The store stage Results produced by ALU are stored in registers Instruction explains which register to use When instruction is completed, the next instruction will be fetched The fetch–decode–execute–store cycle begins again Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 21

Making CPUs Even Faster Building a faster CPU is not easy Must consider time to design, manufacture, and test the processor For release in 36 months, a CPU must perform twice as fast as currently available Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 22

Making CPUs Even Faster Pipelining CPU works on more than one stage or instruction at a time Boosts CPU performance System clock indicates when instructions move to next process Can potentially run four times faster Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 23

Making CPUs Even Faster Pipelining Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 24

Making CPUs Even Faster Specialized Multimedia Instructions Incorporates specialized multimedia instructions in the command set Speeds up video and audio processing Advanced Encryption Standard (AES) Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 25

Making CPUs Even Faster Multiple Processing Efforts Many high-end server systems use a large number of processors Multicore processing Quad-core processors have four separate parallel processing paths Six- and eight-core processors are available Parallel processing uses multiple computers to work on a portion of same problem simultaneously Copyright © 2017 Pearson Education, Inc. TIF Under the Hood 26

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