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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How does a computer work?
• 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”
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How does a computer work?
• 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
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How does a computer work?
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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
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What do RAM and processing circuitry look like?
• 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
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What do RAM and processing circuitry look like?
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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
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How does data get into chips?
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How does data get into chips?
• 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
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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
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Does a computer use the same code for all types of data?
• 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
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Does a computer use the same code for all types of data?
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Does a computer use the same code for all types of data?
– 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
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Figure 17-5
Does a computer use the same code for all types of data?
– 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
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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
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Technology: Microprocessors
• Manufacturers– Intel• Original chipmaker and
still the largest• Current chip is the Intel
Core i7
– AMD• Current offering includes
the A series
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Figure 17-8
Technology: Microprocessors
• 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
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Technology: Microprocessors
• 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
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Technology: Microprocessors
– 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
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Technology: Microprocessors
– 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
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Technology: Microprocessors
• 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
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Technology: Microprocessors
• 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
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Technology: Microprocessors
• Windows Experience Index
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