VMS Help START, /CPU, Examples  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    1.$ START/CPU

      The START/CPU command in this example selects a single inactive
      processor from the set of those processors that are currently
      available but inactive. When it completes its initialization,
      the selected processor becomes part of the system's active set
      and is capable of scheduling and executing processes.

    2.$ START/CPU 4,7

      The START/CPU command in this example selects the processors
      with CPU IDs 4 and 7, if they are currently available and
      inactive. When they complete initialization, these processors
      become part of the system's active set and are capable of
      scheduling and executing processes.

    3.$ START/CPU/ALL

      The START/CPU/ALL command in this example selects all
      remaining inactive and available processors. When they
      complete initialization, these processors become part of the
      system's active set and are capable of scheduling and executing
      processes.