VMS Help FORTRAN, /MATH_LIBRARY, V5  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Controls whether the compiler restricts its use of math library
  routines to those provided in OpenVMS VAX V5.4.  If V5 is
  specified, the compiler does not use optimized versions of the math
  library routines for scalar references to the AMOD, ATAN, ATAN2,
  CABS, CCOS, CEXP, CLOG, COSH, CSIN, CSQRT, SIGN, SINH and TANH
  intrinsic functions nor does it vectorize references to the ATAN2,
  CCOS, CEXP, COSH, CSIN, CSQRT, MOD, SINH and TANH intrinsic
  functions.  The default is NOV5 which enables the above
  optimizations and vectorizations, making use of new math library
  routines which are provided with the Compaq Fortran 77 product but which
  are not present in OpenVMS VAX versions V5.4 through V6.0.