Library /sys$common/syshlp/sysgen.hlb CONNECT, Qualifiers, /VECTOR_OFFSET  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /VECTOR_OFFSET=value

    For devices on multiple device boards, specifies the offset from
    the interrupt vector address of the multiple device board to the
    interrupt vector address for the specific device being connected.
    To specify the address in octal or hexadecimal, precede the
    address with %O or %X, respectively.