In message: <[EMAIL PROTECTED]> Leo Bicknell <[EMAIL PROTECTED]> writes: : In a message written on Fri, Mar 29, 2002 at 06:04:11PM -0600, Paul Halliday wrote: : > I just connected my gps (garmin gps III plus) to my serial port : > and realized that simply cat'ing cua0 displays date/time/position of the : > unit. (neato). Anyway, how accurate would it be to use the time from this : > output for ntp as opposed to my current setup using ntp servers. : : Your NTP servers are better. : : I tested a III Plus, and without a 1 PPS source (which that model : doesn't provide) it's accurate to about 100ms, give or take. Since : real NTP servers are < 1ms, they really aren't that good. It's : not that the time isn't accurate, it's that they were not designed : to communicate with that accuracy to an external device.
Also, the reference clocks that ntp servers use generally are in the +- 1us or better rather than 1ms sync that you can get over a wan. Of course, don't look too closely under the covers of ntp. it has well documented startup transient conditions that some applications may be senentive to. Warner To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-hackers" in the body of the message
