[ntp:questions] Slow convergence of NTP with GPS/PPS

Unruh unruh-spam at physics.ubc.ca
Thu Oct 23 00:56:43 UTC 2008

Rick Jones <rick.jones2 at hp.com> writes:

>Hal Murray <hal-usenet at ip-64-139-1-69.sjc.megapath.net> wrote:

>>   NTP temperature compensation
>>   Mark Martinec, 2001-01-08
>>   http://www.ijs.si/time/temp-compensation/

>> A wonderful read.

>I wonder how closely Mark's results could be replicated using some
>(set of) temperature readings from components already in the system
>rather than adding another temp probe?  Stuff like CPU temps and other
>intra-system components.  I'm not sure they have nearly the same
>accuracy and resolution though :(

The problem is not accuracy and resolution, the problem is time delay. If
the cpu heats up, it will take a while for the clock crystal to heat up and
will not heat up as much. Ie, the cpu could jump to 70C briefly while some
calculation was being done, while the clock crystal heated up almost
nothing. It is probably better than nothing but if the computer has a very
variable useage, so the temp fluctuates a lot, this will be much noisier
than directly measuring the temp of the crystal. If the computer is pretty
stable, it should be fine to use other proxies. 

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