Computing Components

• Goals
  • Read an ad for a computer and understand the jargon
  • List the components and their functions in a von Neumann machine
  • Describe the fex-decode-execute cycle of the von Neumann model
  • Describe how computer memory is organized
  • name and describe different auxiliary storage devices
  • define three alternative parallel computer configurations
• Shopping for your own machine
  • 
  • 
  • From Best Buy's add, Erie Times-News, March 21, 2004

  • Machine	CPU	MEM	HD	Mon	Price
    A	C 2.6 GHz	256 MB	40 GB	17" CRT	$340
    B	C 2.7 GHz	256 MB	80 GB	17" CRT	$390
    C	C 2.8 GHz	512 MB	120 GB	15" LCD	$730
    D	P 2.8 GHz	512 MB	160 GB	15" LCD	$1200
    E	P 3.2 GHz	512 MB	200 GB	17" LCD	$2000

  • Some terms
    • Units
      • bits (b)
      • bytes (B) - 1 byte = 8 bits
      • Hertz (Hz) - is a measurement for frequency
        • 1 Hz = 1 cycle/second
    • Unit prefixes
      • pico (p) = 1x10^-12
      • nano (n)= 1x10^-9
      • micro (u)= 1x10^-6
      • milli (m)= 1x10^-3
      • kilo (K) = 1x10³ (2¹⁰)
      • mega (M) = 1x10⁶ (2 ²⁰)
      • giga (G) = 1x10⁹ (2 ³⁰)
      • tera (T) = 1x10¹² (2 ⁴⁰)
    • What we measure
      • Modern clocks are measured in single GHz
      • Memory is measured in 100s of MB to singe GB
      • Memory speed is measured in 100MHz
      • Disk Space is measured in 10GB to 100s of GB
      • Hard drives sometimes mention RPM,, how fast they turn
      • Network speed is from 4Mb to 1Gb
      • Dial up connections are measured in 10Kb to 56Kb
      • CD (and DVD) drives are measured in x faster than a music CD
    • Why we measure
      • Storage numbers and network numbers give us speed/size comparisons
      • You can never go wrong with more memory/drive space
      • Processor speed is a reasonable comparison only within the same processor family.
      • But other factors come into play
    • Other Considerations
      • Cache
      • Software
      • Audio
      • Graphics Cards
      • Expandability
      • Support and maintanence
    • A final word
      • What are you going to do?
      • How soon will you replace it?
• Stored-Program Concept
  • Sometimes called von Neumann computer
  • Data and program can be stored in the same memory
  • 
  • CPU - Central Processing Unit
    • ALU - Arithmetic Logic Unit
    • MMU - Memory Management Unit
    • Cu - Control Unit
    • Registers
    • PC - Program Counter (IP -Instruction Pointer)
    • IR - Instruction Register
    • Connected via a BUS
  • Memory
    • A bunch of boxes, capible of holding a series of bits
    • Each box has an address (0 - memory size)
    • Usually the number of addresses is a power of two
    • 8,16,32,64, ... bits per address
    • Registers are very fast (CPU Speed)
    • Cache is next, slower but bigger
    • RAM is next
    • Other storage is next
  • Other peripherals
    • I/O
    • Aux storage
    • others
    • Connected via a bus too.
• Fetch Execute Cycle
  • CPU requests the word that is stored at the location indicated by the PC
  • The PC is incremented by 1 instruction
  • Memory returns this value,
  • Value is stored into the IR
  • This is the fetch part
  • The instruction is examined to determin what the computer is to do
  • This is called decode
  • The computer does whatever it needs to do to carryout the instruction
  • This may include getting more data from the memeory
  • Or save data to memory
  • Or add two numbers
  • This is the execute phase.
• Memory
  • Ram VS ROM
    • RAM - Random Access Memory
    • ROM - Read Only Memory
    • PROM/EPROM/EEPROM
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