[ntp:questions] Performance estimation

Miroslav Lichvar mlichvar at redhat.com
Tue Jun 16 13:04:06 UTC 2020

On 2020-06-16, David Taylor <david-taylor at blueyonder.co.uk.invalid> wrote:
> The clock on a Raspberry Pi ranges from 700 to 1500 MHz, so clock 
> resolution is in the nanosecond range.

For best timekeeping performance, you would want to set the CPU
frequency to a fixed value.

> I would also like to see whether the characteristics of the GPS and its 
> location make a measurable difference to the RPi's timekeeping.  For 
> example: is it better to have a GPS with 3 service capability at a 
> location where the signal is poor, or is it masked by the RPi's 
> performance?  All this with kernel-mode PPS.

The interrupt latency of the PPS timestamping is probably much larger
than any errors related to GPS, so I'd say it doesn't matter.

Miroslav Lichvar

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