Practical PC, 7 th Edition Chapter 17: Looking Under the Hood.

Practical PC, 7th EditionChapter 17: Looking Under the

Hood

Looking Under the Hood

• FAQ’s− How does a computer work?−What do RAM and processing circuitry look like?− How does data get into chips?− Does a computer use the same code for all types

of data?

• Technology: Microprocessors

2Practical PC, 7th Edition

How does a computer work?

• A computer works by manipulating data– Data refers to the symbols that describe people,

events, things, and ideas– A computer works with data in four ways:• Accepting input data• Processing data• Producing output data• Storing data

– Input is the data that goes into a computer

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• The computer puts data into RAM (Random Access Memory), a temporary holding area for data– RAM holds data and tells the computer what to do– A computer’s circuitry reads data and processes it– Processing data means manipulating it in some

way, such as performing a calculation– An instruction indicates that data should be

transferred from RAM to a printer, modem, or display screen as output

– Data sent to the hard disk drive is done using a process called “storing data”



• Data is processed in the microprocessor– Control Unit• Gets instructions from computer software

– Registers• Hold data that is being processed

– ALU (Arithmetic logic unit)• Performs arithmetic and comparison operations


What do RAM and processing circuitry look like?

• RAM and processing circuitry are contained in “chips” inside the PC– Chip: nickname for an integrated circuit– Integrated circuit: thin slice of silicon etched with

microscopic circuitry– Microprocessor chip: carries out most of the

processing work on PC– RAM chips: temporarily hold data– ROM (read-only memory) chips: hold the

instructions for PC to boot upPractical PC, 7th Edition 7


• Chip is housed in small, black, rectangular chip carrier which is connected to a circuit board– Circuit board contains electrical pathways

that allow data to travel between chips– In a typical PC, a system board houses the

microprocessor chip, ROM chips, and support chips

– System board is referred to as a motherboard or mainboard


How does data get into chips?

• Data is converted into code and then into electronic signals that travel through circuits on chips and circuit boards– Computer codes are based on ones and zeros– Each 1 or 0 is a bit (short for binary digit)– Eight bits form a byte, which typically form one

character– Data is coded and either stored or transmitted

electronically



• As data is gathered, processed, stored, and transmitted, it is constantly converted from one type of signal to another

– Special controller chips convert the data into different styles of signals

– These chips are found on system boards, graphics cards, sound cards, and modems


Does a computer use the same code for all types of data?

• Computers use different codes for different types of data but all have common characteristics– Digital• A digit is a single character in a numbering system• Data is converted into a finite set of numbers

– Binary• This system uses only two digits, 0 and 1• 0 is “off” and 1 is “on”

– Fixed Length• The same number of bits is used to represent each data

item



• Types of Codes– Text data are stored using ASCII, Extended ASCII,

and Unicode– Numbers for calculations use the binary number

system• Numbers not used for calculations use ASCII, Extended

ASCII, or Unicode



– Bitmap images• Binary color code for each pixel in the image • Simplest code uses three bytes of data. Each byte

defines how much red, blue, and green are in the color


Figure 17-5


– Digital audio• Binary number

represents height of each wave sample• Each sample is stored

as an 8-bit number for radio-quality recordings• High-fidelity

recordings are stored as a 16-bit number


Figure 17-6

Technology: Microprocessors

• A microprocessor is an integrated circuit that is the main processing device in a PC– Most computers contain x86 microprocessors• Ancestry goes back to the first generation of PCs• New x86 processors are faster and more capable but

can still run software designed for the first generation of x86 processors



• Manufacturers– Intel• Original chipmaker and

still the largest• Current chip is the Intel

Core i7

– AMD• Current offering includes

the A series


Figure 17-8


• Clock speed– Contributes to overall system performance– Measured in gigahertz (GHz)− One GHz is 1 billion cycles per second− The faster the clock speed, the more instructions

the processor can carry out in each second



• Factors that affect the microprocessor speed:− Instructions per clock cycle− Processors that execute multiple instructions per clock

cycle are referred to as superscalar

− CPU Cache−Data-holding circuitry that can be accessed faster than

RAM−Measured in kilobytes (KB)• Most of today’s microprocessors have multi-level

caches--L1, L2, or L3



– Accelerated front side bus• Circuitry that moves data to the microprocessor• Moves data quickly--HyperTransport and Quickpath• Allows processor to work at full capacity

– Extended instruction set• Speeds up video or photo processing

– Multi-core architecture• A multi-core processor is a single microprocessor chip

whose circuitry allows more than one instruction to be processed at a time



– Word size• Refers to the number of bits that a microprocessor can

manipulate at one time• Based on size of registers: 64-bit vs 32-bit• Most personal computers contain 64-bit processors• 32-bit processors are used primarily for tablets• Larger word size means more data can be processed

during each processor cycle



• Benchmark test– A set of standard processing tasks that measure

the performance of computer hardware and software

−Microprocessor benchmark tests measure how fast processors perform a set of tasks



• Types of benchmark tests−Multimedia benchmarks measure performance

when processing multimedia data– Integer benchmarks measure processing efficiency

for integer data– Floating-point benchmarks measure performance

for numbers stored in a “floating point” format used in 3-D graphics, computer-aided design, and many computer games



• Windows Experience Index


Practical PC, 7 th Edition Chapter 17: Looking Under the Hood.

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