[ntp:questions] Red Hat vote for chrony

William Unruh unruh at invalid.ca
Mon Dec 8 03:19:39 UTC 2014

On 2014-12-07, Charles Swiger <cswiger at mac.com> wrote:
>> That's why NTP can act as a thermometer.  The big problem is temperature induced wander and that's something (back to RedHat and Chrony) Chrony claims to do better.
> Yes, ntpd and chrony will notice temperature changes causing a frequency drift, at least
> when a system is using cheap AT-cut XOs, which commonly show a temperature-dependency
> frequency variation in the 10s of PPM range for a 10 C change around room temperature.
> A more expensive SC-cut XO will likely remain stable to a few PPM for such a range,
> and a calibrated TCXO or OCXO will do better still.
> I suspect most people are a bit more likely to use air conditioning to control ambient
> temperature changes then they are to desolder and swap out their crystals in the
> hopes of obtaining more precise timekeeping....

Actually air conditioning is largely irrelevant because it is not
ambient air temperature changes that are most important, but temp
changes inside the case caused by differing loads on the system. 

One of my collegues debvised a script whose sole purpose was to stress
the cpus so he could use the air coming out to dry his socks. 
Ie, cpu load drives temp change which produces time shifts. 

And it is there that chrony tends to be better at keeping track of the
rate changes.

> Regards,

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