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Chapter 17Looking “Under the Hood”
2 Practical PC 5th Edition Chapter 17
Getting Started
• In this Chapter, you will learn:− 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
3 Practical PC 5th Edition Chapter 17
Getting Started
• In this Chapter, you will learn (continued):− How does software tie into chips, codes, and
circuits − About Hardware: Microprocessors
4 Practical PC 5th Edition Chapter 17
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
5 Practical PC 5th Edition Chapter 17
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 a process called “storing data”
6 Practical PC 5th Edition Chapter 17
How does a computer work?
Input data arrives in RAM and is processed
7 Practical PC 5th Edition Chapter 17
What do RAM and processing circuitry look like?
• RAM and processing circuitry are contained in “chips” inside 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
8 Practical PC 5th Edition Chapter 17
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
9 Practical PC 5th Edition Chapter 17
What do RAM and processing circuitry look like?
PC System Board
10 Practical PC 5th Edition Chapter 17
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
11 Practical PC 5th Edition Chapter 17
Does a computer use the same code for all types of data?
• Computers use different codes for different types of data– Text data: ASCII, extended ASCII, ANSI, Unicode, or EBCDIC codes– 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
12 Practical PC 5th Edition Chapter 17
Does a computer use the same code for all types of data?
ASCII code: Digital, Binary, and Fixed Length
13 Practical PC 5th Edition Chapter 17
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 in 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
14 Practical PC 5th Edition Chapter 17
Hardware: Microprocessors• Microprocessor is a single integrated circuit• Microcomputer is a type of computer that uses a
microprocessor as its main processing unit, such as your PC• Most microcomputers 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 chips with speeds over 3 GHz
• 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
15 Practical PC 5th Edition Chapter 17
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• Level 1 cache is on the microprocessor chip• Level 2 cache is on a separate chip
− Accelerated front side bus; fast version will move data quickly and will allow the processor to work at full capacity
• HyperTransport is a technique to accelerate the rate data travels on the front side bus
16 Practical PC 5th Edition Chapter 17
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
• Benchmark test is a set of standard processing tasks that measure the performance of computer hardware and software− Microprocessor benchmark tests measure processor speed
17 Practical PC 5th Edition Chapter 17
Hardware: Microprocessors• Benchmark tests measuring processor performance fall into
categories:− Multimedia benchmarks measure performance when processing
multimedia data− Integer benchmarks measure performance when processing words and
numbers used in word processing, presentation, spreadsheet, and database applications
− Floating-point benchmarks measure performance for numbers stored in a special “floating point” format used in 3-D graphics, computer-aided design, and many computer games
− Real-world performance benchmarks measure how well a computer executes a predefined set of tasks while running word processing, spreadsheet, and other productivity software
18 Practical PC 5th Edition Chapter 17
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?
19 Practical PC 5th Edition Chapter 17
Chapter Summary
• You should now:− Understand how a computer works− Know what RAM and processing circuitry look
like− Understand how data gets into chips− Know if a computer uses the same code for all
types of data
20 Practical PC 5th Edition Chapter 17
Chapter Summary
• You should now be able to (continued):− Know how software ties into chips, codes, and
circuits − Understand Microprocessors