The following illustrates the possible system configurations and
    their effect on performance:

    o  CPU1 and CPU2 with VVIEF support:

       Efficent for program development, but can be 3-5 times slower
       than the scalar performance. Cost-effective for parallel
       applications that do not use vector processing.

    o  CPU1 - CPU2 with Vector processor:

       Efficent vector performance: As soon as a processor issues its
       first vector instruction, VMS schedules it only for vector-
       present(VP) CPU2. If the process is executing on CPU1, VMS
       swaps out and gives it to CPU2. If CPU2 is not free, the
       process waits for it to become free: VMS does not use VVIEF
       on this system.

    o  CPU1 and CPU2:

       Fatal to vector programs. They will fail when the first vector
       instruction issues and neither VVIEF nor any other vector
       processors are present.

    o  CPU1 and CPU2 with Vector processors:

       Most efficent parallel-vector performance and cost-effective.

    o  CPU1 and CPU2 - CPU3 and CPU4 with Vector processors:

       Efficent parallel-vector performance.

1  –  VVIEF on VAX Multiprocessors

    If no vector-present CPU is available, OpenVMS executes vector
    instructions using the VAX Vector Instruction Emulator Facility
    (VVIEF), which is much slower than scalar execution.

                                   NOTE

       VVIEF must be enabled on the OpenVMS system; it is disabled
       by default. To enable VVIEF, the system manager must execute
       the command file SYS$UPDATE:VVIEF$INSTAL.COM. For more
       information, refer to your OpenVMS documentation set.