1.1

• What does CPU stand for?

  Central processing Unit
• FDE cycle -

  Fetch - CPU fetches an instruction from main memory

  Decode - CPU decodes the instruction

  Execute - CPU executes the instruction
• What affects the performance of the CPU?

  • Clock speed
  • Cache size
  • Cores
• Clock Speed -

  • measured in Hertz
  • number of cycles per second
  • higher clock speed means more FDE cycles per second
• Cache -

  • Temporary storage of data and instructions being read and written
  • stores copies of recent data and instructions
  • CPU has faster access than RAM
  • too much can be detrimental
• Cores -

  • complete copy of CPU
  • quad core processor would have 4 separate processing units
  • each core works independanty
• What is an embedded system?


  A system which is built into a larger system with a specific pupose
• Advantages of embedded systems -

  • low power consumption
  • do not need updating
  • small size
  • rugged operating systems
  • low cost per unit
• Embedded system examples -

  • washing machine
  • dishwasher
  • microwave
• Control Unit -

  sends signals to control flow of data and oversees FDE cycle
• Arithmetic Logic Unit -

  performs arithmetic calculations and logic operations
• Cache -

  high speed small storage memory, stores frequently used data and instructions
• What are registers?

  Temporary storage locations within the CPU
• Program Counter - 


  holds memory address of next instruction to be carried out
• Memory Address Register - 


  stores the memory address of instruction being searched for
• Memory Data Register - 


  holds instructions that are to be read/written to memory
• Accumulator -


  holds the result of calculations performed by the ALU