Transcript Chapter 17

Practical PC, 7th Edition
Chapter 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
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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:
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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
instructions for PC to boot up
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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
Figure
17-5
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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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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
Figure
17-8
• Current offering includes
the A series
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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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