On Mon, Apr 18, 2011 at 3:49 PM, unruh <un...@wormhole.physics.ubc.ca> wrote:
>> Thanks for all the great answers. Now for a harder question, how does the >> accuracy of the local clock source >> affect the accuracy of ntpd. > > What local clock source? That is a good question: "Which clock?" One clock might be the reference clock for a stratum 1 NTP server. This is typically a GPS receiver and these vary a LOT. Some can supply a pulse per second with 1 sigma error of only a hand full of nanoseconds and other GPSes have hundred of microseconds of error. That is a factor of over 10,000 difference in accuracy. The other clock is the crystal inside the computer that NTP tries to "discipline" by using the above reference clock. I think what matters most is "stability" rather than "accuracy". In other words it is fine if this oscillator runs at the wrong speed but not good if the speed is not constant with respect to time. The best oscillators are housed in temperature controlled ovens but these are not common inside PCs. -- ===== Chris Albertson Redondo Beach, California _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
