Darren Dunham wrote:
> In comp.unix.solaris Dave <someplace@nowhere-nice.com> 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?
>
> Can you simulate the conditions beforehand (with net access)? Run NTP,
> get them all synced up. Enable logs and make sure you have driftfiles
> in place.

One problem is I don't currently have both machines. However, I will be
able to do some testing in this way.

> On the client "disable ntp" in the config file so that polls are done,
> but the clock is not modified. Let it run that way in simulated
> conditions and see what your drift rate is.
>
> Temperature will likely be the biggest factor in frequency changes.

Yes, and I suspect that it could be quite significant.
>
> If temperature is somewhat stable, 500ms should be achievable for a few
> days.
>

I only need it for 4 hours. 500 ms in 4 hours equates to 34.7 ppm, which
is probably expecting a bit much when crystals are not at similar
temperatures.

I thought at first that GPS was not going to be possible, but I'm now
told it might be.

Anyway, lots of people have given me lots of ideas.