Re: [chrony-dev] Frequency synchronization without phase

[Miroslav Lichvar <mlichvar@xxxxxxxxxx>]

On Tue, Dec 06, 2016 at 09:54:41PM -0600, Dan Drown wrote:
> After 7 days: https://dan.drown.org/odroid/run5.7/tempcomp.png
> 
> It looks like tempcomp is helpful but maybe my reference is drifting.  I
> want to try this again with a better TCXO.

Ok, thanks for the data.

> I setup a quick benchmark of heating the CPU and on-board crystal with a
> bunch of cpu wasting processes.  CPU core went from 51C to 70C (as measured
> by the on-CPU temperature sensor):
>
> https://dan.drown.org/odroid/run5.7/tempcomp-cpuheating.png
> The test of cpu heating actually turned out pretty well.  The tempcomp moves
> ~400ppb while the tracking moves less than 100ppb.  The offset stays within
> +/- 25us during this time (with a poll of its stratum 1 at 64s).

So this was with 16s tempcomp update interval? I think with a shorter
interval it might be even better. If your system is anything like
mine, 16s would be too long to deal with spikes in the frequency when
the CPU is loaded for short intervals. In this plot the frequency
changes by more than 300 ppb in 30 seconds and then it takes about 2
minutes to cool down.

http://i.imgur.com/7rZJslH.png

-- 
Miroslav Lichvar

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