[ntp:questions] Raspberry Pi error in PPM offset

unruh unruh at invalid.ca
Fri Aug 23 03:40:04 UTC 2013

On 2013-08-23, JP <james.peroulas at gmail.com> wrote:
> I have access to an accurate frequency counter that I use to measure the Pi's actual crystal frequency. I find that the PPM error reported by NTP differs from the real PPM error consistently by about 2.5 PPM. i.e. when measured over a time period of several days, the difference between the actual PPM error and the reported PPM error varies slightly above and slightly below 2.5 PPM.

What PPM error? What is your reference clock? ntp does not measure a
rate error. It measures offsets and adjusts the rate to eliminate those

> I'm suspecting that there is a configuration issue in the RPi kernel, but, being new to NTP, I'm not sure where to begin looking. Any suggestions?

First tell us exactly what you are doing and measuring. How do you get
that "2.5PPM". What is your ntp server?

> Thanks,
> James

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