CPU components (Comp Sci)

• CPU


  Central processing unit – job is to process data / carry out instructions & execute them
• Benefits of having more cores

  • Cores can work together on same task at the same time
  • Cores can work on different tasks (multitasking) at the same time
  • More instructions can be carried out
  • Instructions can be carried out quicker
• Clock speed


  Number of cycles per second
• Von Neumann Architecture


  • Type of CPU that stores instructions & data in memory
  • Instructions are fetched, decoded and executed
  • There is a single control unit
  • Interacts with input and output devices
• Parts of the CPU

  • Controller Unit (CU)
  • Arithmetic Logic Unit (ALU)
  • I/O Controller Unit
• Controller Unit (CU)


  • Controls the flow of data within the CPU between registers
  • Controls the timing of signals sent within the CPU
  • Decodes instructions
• Arithmetic Logic Unit (ALU)


  • Perform arithmetic calculations (+ * - /)
  • Perform logical operations (AND, OR, NOT)
• I/O Controller Unit


  Controls the communication between input and output devices with the CPU
• 3 units of Von Neumann Architecture

  • Control Unit (CU)
  • Arithmetic Logic Unit (ALU)
  • I/O Controller Unit
• What is the Von Neumann Architecture?

  
  

  It is a design model for a stored-program digital computer that uses a processing unit and a single separate storage structure to hold both instructions and
• Processor Registers


  • Very small and very fast bits of memory in the processor
  • Allows the CPU to work very quickly
• 5 processor registers to learn

  • Program Counter (PC)
  • Memory Address Register (MAR)
  • Current Instruction Register (CIR)
  • Memory Data Register (MDR)
  • Accumulator (Acc)
• Current Instruction Register (CIR)

  Stores the current instruction that has been fetched from memory
• Program Counter (PC)


  Stores the address of next instruction to be fetched from memory
• Memory Address Register (MAR)


  Stores the address of data OR instruction about to be used
• Memory Data Register (MDR)


  Holds data OR instructions that have been fetched or written to memory
• Accumulator (Acc)


  Stores value currently being worked on OR result of last instruction
• Bus


  • A system bus sends data to and from the CPU & RAM
  • These are the wire strips on the motherboard
• 3 types of buses

  • Control bus
  • Address bus
  • Data bus
• Control bus


  • Sends signal to say if data has been fetched or saved to memory
  • 1 way system – CPU > Memory
• Data bus


  • Sends and retrieves data and instructions
  • 2 way system – CPU > Memory & Memory > CPU