[ntp:questions] drift modeling question

Bill Unruh unruh at physics.ubc.ca
Sat Jul 12 01:00:09 UTC 2008

shy author <shy.author.not at aol.com> writes:

>Has anyone thought about removing both the linear terms and quadratic 
>terms in the drift, by utilizing the temperature sensor readings 
>available on many of the latest motherboards?

>Crystal oscillators tend to have both a linear bias and a quadratic bias, 
>determinate upon temperature, leaving a stochastic component, which I 
>believe we're trying to compensate for all along by the operation of ntp.

>Integration of the temperature readings and knowledge of the current 
>drift should suggest the appropriate coefficients for the corrections.

>Just a thought, but it seems a shame that we're not taking advantage of 
>the thermal data available to us, when correcting for clock drift and 
>simply using a linear correction.

A Quadratic correction tends to run away pretty badly if you suddenly have
a period of no ntp readings. But I am not at all sure that is what you
mean. Rather you seem to mean that one use the temp to estimate what the
linear drift is ( from the past readings of temp and drift.)

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