rpi3 clock drift

[Ross Alexander]

On Fri, 29 Nov 2019, Ian Lepore wrote:

> On Thu, 2019-11-28 at 23:51 -0700, Ross Alexander wrote:
>> On Fri, 29 Nov 2019, Peter Jeremy wrote:
>>
>>> [...]
>>
>> BTW, another *significant* source of jitter is the brand and age of
>> the sd/mmc card used. [...]
>
> I'm having a real hard time with this one, conceptually.  This is
> exactly what every one of our products at $work does:  precision timing
> including ntpd and kernel time tracking UTC(GPS) to within a few nanos.
> We've had products in the field for 15 years still using the original
> sdcard and still hitting the same on-time performance numbers as the
> day they were shipped (tracking UTC(GPS) +-10ns RMS).

This is purely empirical.  $WORK machine got jitterier and jitterier.
Copied old SD card onto new SD card (straight dd, not a tar/untar),
problem went away.  Beats me, but thats how it went.

regards,
Ross

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Ross Alexander, (780) 675-6823 desk / (780) 689-0749 cell, rwa at athabascau.ca
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