/ARCHITECTURE=option
       /ARCHITECTURE=GENERIC (D)

    Determines the Alpha or Intel processor instruction set to be
    used by the compiler. The /ARCHITECTURE qualifier uses the same
    keyword options (keywords) as the /OPTIMIZE=TUNE qualifier.

    Where the /OPTIMIZE=TUNE qualifier is primarily used by
    certain higher-level optimizations for instruction scheduling
    purposes, the /ARCHITECTURE qualifier determines the type of code
    instructions generated for the program unit being compiled.

    OpenVMS Version 7.1 and subsequent releases provide an operating
    system kernel that includes an instruction emulator. This
    emulator allows new instructions, not implemented on the
    host processor chip, to execute and produce correct results.
    Applications using emulated instructions will run correctly, but
    may incur significant software emulation overhead at runtime.

    All Alpha processors implement a core set of instructions.
    Certain Alpha processor versions include additional instruction
    extensions.

    Select one of the /ARCHITECTURE qualifier options shown in the
    following table.

    Option                Usage

    GENERIC               Generates code that is appropriate for all
                          processor generations. This is the default.
    HOST                  Generates code for the processor generation
                          in use on the system being used for
                          compilation.

                          Running programs compiled with this option
                          on other implementations of the Alpha
                          architecture may encounter instruction-
                          emulation overhead.
    ITANIUM2 (I64 only)   Generates code for the Intel Itanium 2
                          processor family. For use on I64 systems
                          only.
    EV4 (Alpha only)      Generates code for the 21064, 21064A,
                          21066, and 21068 implementations of the
                          Alpha architecture.

                          Programs compiled with the EV4 option run
                          without instruction-emulation overhead on
                          all Alpha processors.
    EV5 (Alpha only)      Generates code for some 21164 chip
                          implementations of the Alpha architecture
                          that use only the base set of Alpha
                          instructions (no extensions).

                          Programs compiled with the EV5 option will
                          without instruction-emulation overhead on
                          all Alpha processors.
    EV56 (Alpha only)     Generates code for some 21164 chip
                          implementations that use the byte and word-
                          manipulation instruction extensions of the
                          Alpha architecture.

                          Running programs compiled with the EV56
                          option might incur emulation overhead on
                          EV4 and EV5 processors, but will still
                          run correctly on OpenVMS Version 7.1 (or
                          higher) systems.
    PCA56 (Alpha only)    Generates code for the 21164PC chip
                          implementation that uses the byte- and
                          word-manipulation instruction extensions
                          and multimedia instruction extensions of
                          the Alpha architecture.

                          Programs compiled with the PCA56 option
                          might incur emulation overhead on EV4,
                          EV5, and EV56 processors, but still run
                          correctly on OpenVMS Version 7.1 (or
                          higher) systems.
    EV6 (Alpha only)      Generates code for the 21264 implementation
                          of the Alpha architecture.
    EV68 (Alpha only)     Generates code for the 21264/EV68
                          implementation of the Alpha architecture.
    EV7 (Alpha only)      Generates code for the EV7 implementation
                          of the Alpha architecture.

    See also /OPTIMIZE=TUNE, which is a more typical option.
    Note that if /ARCHITECTURE is explicitly specified and
    /OPTIMIZE=TUNE is not, the tuning processor defaults to the
    architecture processor; for example, /ARCHITECTURE=EV6 implies
    /OPTIMIZE=TUNE=EV6.