Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!usc!elroy.jpl.nasa.gov!lll-winken!ames!sgi!vjs@rhyolite.wpd.sgi.com From: vjs@rhyolite.wpd.sgi.com (Vernon Schryver) Newsgroups: comp.sys.sgi Subject: Re: External clock for P-I serial port? Message-ID: <78445@sgi.sgi.com> Date: 17 Dec 90 18:17:07 GMT References: <1990Dec15.003528.11439@ecf.utoronto.ca> Sender: guest@sgi.sgi.com Distribution: comp Organization: Silicon Graphics, Inc., Mountain View, CA Lines: 29 > 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@sgi.com