TIMER REQUEST
        A time request is a non standard IO request.  it has an iorequest
        followed by a timeval structure or an eclockval structure.

   TIMEVAL
        A timeval structure consists of two longwords.  the first is
        the number of seconds, the latter is the fractional number
        of microseconds.  The microseconds must always be "normalized"
        e.g. the longword must be between 0 and one million.

   ECLOCKVAL
        A eclockval structure consists of two longwords.  The first is
        the high order 32 bits of a 64 bit number and the second is the
        the low order 32 bits.  The 64 bit number is a count of "E" clock
        ticks.  The "E" clock frequency is related to the master clock
        frequency of the machine and can be determined by calling the
        readeclock() library like call.

   UNITS
        The timer contains five units -- two designed to accuratly measure
        short intervals, one that has little system overhead and is very
        stable over time, and two that work like an alarm clock.

   UNIT_MICROHZ
        This unit uses the programmable timers in the 8520s to keep track
        of its time.  It has precision down to about 2 microseconds, but
        will drift as system load increases.  The accuracy of this unit
        is the same as that of the master clock of the machine.  This unit
        uses a timeval in its timerequest.

   UNIT_VBLANK
        This unit uses a strobe from the power supply to keep track of its
        time or the "E" clock on machines without power supply strobes.
        It is very stable over time, but only has a resolution of that of
        the vertical blank interrupt.  This unit is very cheap to use, and
        should be used by those who are waiting for long periods of time
        (typically 1/2 second or more).  This unit uses a timeval in its
        timerequest.

   UNIT_ECLOCK
        This unit is exacly the same as UNIT_MICROHZ except that it uses
        an eclockval instead of a timeval in its timerequest.

   UNIT_WAITUNTIL
        This unit waits until the systime is greater than or equal to the
        time in the timeval in the timerequest.  this unit has the same
        resolution and accuracy as that of UNIT_VBLANK.

   UNIT_WAITECLOCK
        This unit waits until the E-Clock value as returned by readeclock()
        is greater than or equal to the eclockval in the timerequest. this
        unit has the same resolution and accuracy as that of UNIT_ECLOCK.

   LIBRARY
        In addition to the normal device calls, the timer also supports
        several direct, library like calls.

   BUGS
        In the V1.2/V1.3 release, the timer device has problems with
        very short time requests.  When one of these is made, other
        timer requests may be finished inaccurately.  A side effect
        is that AmigaDOS requests such as "Delay(0);" or
        "WaitForChar(x,0);" are unreliable.