[ntp:questions] refclock on Windows graphs
David J Taylor
david-taylor at blueyonder.neither-this-bit.nor-this.co.uk
Wed Mar 18 07:28:19 UTC 2009
> "David J Taylor"
>> Another PC in the same room running a FreeBSD system has about half
>> the jitter, but far less offset - PC Pixie at the top:
> That looks much more like the kind of timing I get on my Linux system.
> driven by a PPS from a Garmin 18LVC.
> I assume that the rate is also far more constant on that system.
Not far more constant, no. On the FreeBSD/Pentium-133 system over the
last 72 hours the frequncy varied between about -0.6ppm to +0.4ppm from
the mean, and on the Windows XP system from about -1.4ppm to +1.1ppm from
the mean. So about 1ppm variation as opposed to 2.5ppm, about 40% of the
As far as I can tell, the NTP offset is more a function of the control
loop parameters than of the actual hardware (with ~150us offsets and yet
only 2.5us jitter).
There is another issue - version numbers. The FreeBSD runs 4.2.0-a from
May 2005, the Windows 4.2.4.p6 from 2009. I don't know whether there may
have been internal changes affecting the offset compared to the jitter.
I have checked for a temperature monitoring SNMP plug-in, but not found a
compatible one as yet.
Yes, it would be helpful to have more Windows testers.
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