VMS Help Sys Parameters, PHYSICAL_MEMORY  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    (Alpha only) PHYSICAL_MEMORY specifies the amount of physical
    memory available for use. The default setting is -1, which
    equates to all memory in the system. Decreasing this parameter
    allows you to test smaller configurations of memory without
    having to remove memory boards.

    This special parameter is used by Compaq and is subject to
    change. Do not change this parameter unless Compaq recommends
    that you do so.

    PHYSICAL_MEMORY is an AUTOGEN parameter.