Richard B. Gilbert wrote:
> Dave wrote:
>> I have a requirement where I need two Suns (both Netra T1s) to have
>> their clocks close to each other during an experiment that lasts 4
>> hours. During this time, neither Sun will have internet access and
>> they will not be networked to each other.
>>
>> I suspect if I sync them by NTP before the experiment starts, then
>> they will not drift by more than 500 ms over a 4 hour period. Does
>> that seem reasonable? Has anyone actually ever made medium term (few
>> hours) stability measurements of the clocks in Suns?
>
> Ntpd stores the frequency error of the clock in the drift file if you
> configure a drift file. Most systems have a drift of less than 100 PPM
> in absolute value. Some systems do a lot better than that; 25 or 30
> PPM. Configure your drift file if you haven't already and see what the
> frequency error is.
>
> The systems will do better if you keep tight control of the temperature.

That is definately not possible. One is going to be outside.

>
> If you leave ntpd running on both systems, it will continue to
> discipline the clocks based on the last information it had. If the
> temperature remains stable the clocks should remain very close to each
> other
>

In which case NTP might make matters worst than no NTP during the
experiment.