VM Faults

  If a desired virtual page is not found in physical memory
    A page fault is generated.

    The cpu pauses execution of program.

    VM support circuitry searches the Virtual page table
      for an open frame.

      If all frames in use
        An existing page must be purged.

        If dirty bit set
          Old page is first written to disk.

    The desired page is fetched and stored in purged frame.
   
    The cpu then re-runs the faulted instruction.