Lectures
CPU's internal system.  

  Control unit - circuitry used to coordinate the correct functioning of 
    the cpu.  Usually invisible to user

    Clock used to synchronize the advancing of the state machine.
       (Executing task in small discrete steps).
    Other overhead signals - such as specifying data direction.
    Cache implementation.
    Virtual memory implementation.
      etc.
    Interrupt handling - processing of task exceptions.
      Hardware interrupts.

  Datapath - circuitry used to perform task specified by user provided 
  instructions and data.

    Calculating units
      Arithmetic logic unit - ALU - does most calculating.
      Instruction decoder - interprets instructions and sequences execution.

    Work memory
      Registers to hold data for processing.
      Registers used as counters.
      Registers to hold control and status flags.
      Registers to hold target memory addresses.
  
    I/O
      Address and data bus. 

    * Software interrupt processing - standard OS library functions provided
      to simplify and standardize programs access to hardware (read keyboard,
      write to storage, write to display ).
    
Synchronous timing and fetch execute (vonNeumann) cycle.
  Fetch/execute cycle

  Clock used to ensure that circuits a stable state between each step of
  the fetch execute cycle.