Several libpf functions require high-resolution timing information.
  On most recent machines (Indy, Indigo, Indigo2, 4D/35 and Onyx) and
  PowerSeries or Crimson machines with IO3 boards, IRIS Performer
  uses special hardware counters with sub-microsecond resolution.
  (The IO3 board was standard on Crimson and later 4D/300 and 4D/400
  machines. You can check for it with the hinv(1M) command.)

  On older platforms, for example, those with IO2 boards, the
  time-of-day clock is used, which, by default, has a 10 ms
  resolution. This resolution is inadequate for many libpf functions,
  including animation sequences (pfSequence), graphics load
  computation (pfChanStress), and the display of accurate channel
  statistics (pfDrawChanStats). On these machines, you may want to
  enable fast timers using systune(1M) to set the fasthz variable.
  See the man page for timers for more information. Frame rate
  control is poor on machines that lack both a fast clock and the
  video clock used by pfVClockSync.