On 2012-02-24, David Lord <sn...@lordynet.org> wrote: > unruh wrote: >> On 2012-02-23, Alby VA <alb...@empire.org> wrote: >>> On Feb 23, 4:29?pm, unruh <un...@invalid.ca> wrote: >>>> No, that is a very typical figure for the frequency offset. Remember >>>> that the crystals used to control the timing in computers are not >>>> supposed to be terribly accurate. (They are chosen to be cheap, not >>>> great). >>>> It is because such frequency offsets exist that ntp was invented to >>>> correct. >>>> >>> >>> >>> When you say "crystals used to control the timing in computers", >>> are you referring to the parts that make up my actual FreeBSD >>> Server (ie: Motherboard)? Or Parts in the GPS Device (ie: Sure Elec. >>> GPS)? >> >> On your motherboard. >> >> >>> Or in the Satellites receiving the GPS signal? >>> >>> I'm just trying to gauge, what hardware should be looking to obtain >>> to >>> improve that frequency offset. Or is it a moot point unless I'm going >>> to >>> invest in some high dollar atomic clock? >> >> An atomic clock. >> >>> Or better yet, can I buy quality crystals from DigiKey and do some >>> soldering in whatever devices that need crystal upgrading? >> >> No. >> >> And why do you care? As I said this is waht ntp was invented for. It is >> doing its job. > > When I started using ntpd it didn't work with some of my > systems as the clocks were too far out, >> 50ppm, and/or
Do you mean >500PPM? If you were running linux, you could use the adjtimex program and the -t or --tick adjustment to change the tick value of your system clock. each value of 1 adjustment speeds up or slows down the clock by about 100PPM. You can use that to get the clock within the +- 500PPM range that ntpd can adjust. chrony uses it automatically. > too temperature sensitive. Some of my motherboards had a > 3-pin jumper already fitted so that an external clock > source could be connected. Temperature sensitivity is usually in the "less than 1PPM per degree C" so you would have had to be expriencing quite a heat wave (500 degrees C) to have temperture be a factor. I suspect other things might have been more urgent worries then. > > One of my desktop systems, p4-2667, has just taken two > days to get to an offset of under 2 ms after a kernel ntpd is slow, but not that slow. Since for greater than 128ms offset it does a step, and since it fixes things by about 1/2 per hour, half a day is more like it to get it down to microsecond, not millisecond ranges. > change. I suspect because that coincided with the hottest > day in February since 1998. All my pcs were affected > except the one connected to PPS from a Sure GPS. The one > with an MSF source, no PPS, was also fighting to keep sync. It sounds to me like network problems and ntp server problems were playing a role. > > > David > > >> Note that even all of the time standard labs around the world use >> programs like ntp to track their frequency offsets. >> And all atomic clocks have them. >> >> >>> _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions