External clock for P-I serial port?

[Vernon Schryver]

> I am wondering why you need an external clock?  gettimeofday() provides
> time in micro-second.  

While the resolution of gettimeofday() is in microseconds, its accuracy is
only that of the system clock, which is usually 10 milliseconds but can be
set to about 1 millisecond.  That is, while getttimeofday() may return an
odd number of microseconds, that number will change only every 1 or 10
milliseconds.


Perhaps the originial question concerned an alternative to timed,
timeslave, or NTP.  If so, an external time-of-day clock can be connected
via a built-in serial port to synchronize the system clock with something
external.  For example, the timeslave command (see timeslave(1M)) can talk
to a "Precision Standard Time" WWV receiver.  PST went out of business, but
rumor has it that the new owners, "Traconex", can be reached at:

	Robert Young
	1140 N. Kramer Blvd.
	Unit G
	Aneheim, CA  92806
	(714) 632-9510

There are rumors that GEOS "satelite clocks" have been connected as well.



Vernon Schryver,   vjs at sgi.com