Post on 11-Jan-2016
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Intro to Info TechSystem Unit
Copyright 2003 by Janson Industries
This presentation can be viewed on line at: http://web.fscj.edu/Janson/cgs1060/wk05.SystemUnit.ppt
Copyright 2012 by Janson Industries2
Objectives
▀ Explain the system unit and processing unit's components
▀ Explain how the components work together
Copyright 2012 by Janson Industries3
System Unit▀ Different types of computers will
have different components
▀ Hand-held will have all components in System Unit♦ Monitor, Keyboard, Pointer, etc
▀ PC's System Unit has storage devices but Mainframes don't ♦ Secondary Storage is physically
separated from the MF System Unit
Copyright 2012 by Janson Industries4
System Unit▀ Definition:
♦ The h/w that houses the processing unit components
▀ In desktop PCs: ♦ Usually a plastic or metal box that also
contains non-processing components like drives
♦ Processing components are stored on a mother board
● This is also often true for larger and smaller computers
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System Unit▀ Comprised of:
♦ CPU♦ Internal Memory♦ Expansion Slots ♦ Bus♦ Ports
▀ Lots of different internal memory♦ RAM♦ ROM♦ Flash
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Internal Memory▀ RAM: Random Access Memory
♦ Volatile, chip based♦ Commonly known as Main
Memory♦ Holds programs and data that are
currently being worked on
▀ ROM: Read Only Memory♦ Non-volatile, chip based♦ Holds the most basic instructions
of the computer
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Internal Memory Flash
Non-volatile, chip based Doesn’t need electricity to retain info Holds computer start up instructions
and system info System time, date
Chip based memory is fast 200,000 X faster than a hard drive
Approx 10 nanoseconds to retrieve data
Also measured by size Mega/Gigabytes (m/billions of bytes)
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Memory Size▀ Byte = 8 bits = 2 nibbles
▀ A character can be represented with one byte
▀ Lots a different Binary Representation Systems♦ EBCDIC♦ ASCII♦ Unicode
● Gather round. I want to tell you about Snow White and the 7 dwarfs....
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Internal Memory▀ System Unit may have many RAM
chips, Flash chips, etc.♦ Total RAM usually gigabytes (billions)♦ Usually can add more to your system
▀ Often some RAM etched onto same chip as the CPU♦ Speeds up access
''
▀ Can have specialty memory♦ i.e. memory that stores and retrieves
video, images faster
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Internal Memory▀ Many chips stored on a module
♦ Module is a 3 dimensional circuit board
▀ Module stored on board/card
▀ Board/card goes into a expansion slot and (often) snaps into the mother board
▀ Lots of different cards to add or enhance functionality♦ Video card, sound card, network card
''
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CPU▀ To understand IM, must understand
how the CPU works with it♦ Book diagram (Fig 4-4) is misleading
▀ CPU on a single chip (called a microprocessor), comprised of 2 pieces:♦ CU – Control Unit♦ ALU – Arithmetic Logic Unit
▀ Can have multiple CPUs and/or multiple CPU's on a chip
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CPU▀ CU manages all communication
and memory
▀ ALU does math and comparisons
Disk Drive
Main Memory
CPU
Monitor
Keyboard
CU
ALU
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The Machine Cycle▀ The steps the CPU goes through to
perform one instruction♦ Get instruction from MM – CU♦ Decode the instruction and send to
the ALU – CU♦ Instruction performed – ALU♦ Instruction result moved into MM – CU
▀ The next instruction might be "display the result" or "save the result on disk"
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Suppliers For PC's, Intel (IBM chose their
chip/design in 1980) 8086, 286, 386, 486, Pentium,
Itanium, etc. Lots of clones: AMD, Transmeta
IBM: Supercomputers, MFs, game consoles
Motorola: communication devices
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Suppliers For mobile devices, ARM (Advanced
RISC Machine) chips used Intel chips are CISC (Complex
Instruction Set Computer)
ARM chips have lower power consumption so majority of mobile devices use them to extend battery life
Windows 8 runs on ARM ARM mfgs will be going after PC and server
market!
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CPU Measured by speed
Lots of different methods Clock speed measures how many
cycles are completed per second Cycle = hertz Gigahertz = 1 billion cycles/second
Mfgs will argue about what can be done in a cycle FLOPS – Floating Point Operations Gigaflops, Teraflops
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Ports Essentially sockets for connecting
peripheral devices Serial - one bit at a time Parallel – multiple channels USB (Universal Serial Bus)
Connects many types of devices Lots of other specialty ports:
Head phone Microphone Telephone
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Ports Limited number of ports on a
computer Hubs allow you to connect many
devices to a single port
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Bus The wiring that connects all the
processing unit components Ports to the CPU The CPU to Main Memory Expansion slots to the CPU
Larger computers can have multiple buses
Measured by How many bits at a time (64 bit bus) Clock speed (1 GHz)
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System Unit PCs also have bays
System Unit opening that can hold a device
Internal and External Internal holds Hard drive External holds CD, DVD drive
Laptop may have only 1 bay Can slap in a CD, Floppy, or
DVD drive
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What do you need?
What do you want to do with the computer?
This dictates application s/w
Application s/w dictates: OS H/W – memory, video card Peripherals
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Points to Remember▀ System Unit houses the processing
components of a computer
▀ In PCs, will also have secondary storage devices
▀ Many factors determine a computer's speed♦ Chip speed, bus speed, amount of
internal memory