Transcript Chapter 17: Looking “Under the Hood”

Chapter 17
Looking “Under the Hood”
Getting Started
• FAQs:
− 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?
− How does software tie into chips, codes, and circuits?
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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:
• Accepting input data
• Processing data
• Producing output data
• Storing data
– Input is the data that goes into a computer
• The computer puts data into RAM (Random Access Memory),
a temporary holding area for data
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How does a computer work?
• 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?
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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 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
• Circuit board contains electrical pathways that allow data to
travel between chips
• In a typical PC, a large circuit board houses the
microprocessor chip, ROM chips, and support chips
• Series of RAM chips are connected to a small circuit board
called a memory module
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What do RAM and processing
circuitry look like?
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How does data get into chips?
• PC works with data converted into code and then into
electronic signals that travel through circuits on chips and
circuit boards
– Computer codes are based ones and zeros
– Each 1 or 0 is a bit (short for binary digit)
– Eight bits form a byte
• Data is coded to transmit electronically
• As data is gathered, processed, stored, and transmitted,
special controller chips constantly convert it from one type of
signal to another
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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
– Text data: ASCII and Unicode
– Numbers for calculations: binary number system
– Bitmap images: binary color code for each dot
– Recorded sound: binary number represents height of wave
sample
• Codes share characteristics
– Digital: converts data into a finite set of numbers
– Binary: uses only 0s and 1s
– Fixed length: use the same number of bits to represent
each data item
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Does a computer use the same
code for all types of data?
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How does software tie into chips,
codes, and circuits?
• Software is a collection of programs or program modules
containing a list of instructions
– Instructions are written using a computer programming
language
– Today’s programming languages use English-like words
– English-like words must be converted into a machine
language of 1s and 0s
• Compiling is the process of converting English-like words into
1s and 0s
– Compiling creates executable EXE files
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How does software tie into chips,
codes, and circuits?
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Hardware: Microprocessors
• Microprocessor is a single integrated circuit
• Most computers contain x86 microprocessors
− Able to work with the x86 instruction set
− Intel is the original x86 chipmaker and is still the largest
− Both Intel and AMD offer x86 microprocessors
• Clock speed is measured in megahertz (MHz) or gigahertz
(GHz)
− One MHz is 1 million cycles per second and one GHz is 1
billion cycles per second
− Clock speed is analogous to how fast you pedal a bike.
Faster cycles mean faster computer processing
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Hardware: Microprocessors
• Several factors can affect the speed at which a microprocessor
processes instructions
− Instructions per clock cycle: Processors that execute
multiple instructions per clock cycle are referred to as
superscalar
− Cache memory is data-holding circuitry that can be
accessed faster than RAM
• Most of today’s microprocessors have multi-level caches
• L1, L2, or L3 caches
− Accelerated front side bus; fast version will move data
quickly and will allow the processor to work at full capacity
• HyperTransport and QuickPath
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Hardware: Microprocessors
• Several factors can affect the speed at which a microprocessor
processes instructions (continued)
− Extended instruction sets: some processors have this
feature to speed up certain types of processing
− Multi-core architecture: multi-core processor is a single
microprocessor chip with circuitry that allows it to process
more than one instruction at a time
− Word size: refers to the number of bits that a
microprocessor can manipulate at one time
• Benchmark test is a set of standard processing tasks that
measure the performance of computer hardware and software
− Microprocessor benchmark tests measure processor speed
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Hardware: Microprocessors
• Benchmark tests measuring processor performance fall into
categories:
− 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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Who invented the first electronic
digital computer?
• What do you think?
– Do you think the judge made the right decision, despite the
fact that Atanasoff never filed for a patent?
– Do you think that Zuse, instead of Atanasoff, should be
declared the inventor of the first electronic digital
computer?
– Do you think that the computer industry would be different
today if Sperry Rand had won its patent case?
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