| Re: [chrony-users] SatPulse: server-oriented alternative to gpsd for chrony |
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- To: James Clark <jjc@xxxxxxxxxx>
- Subject: Re: [chrony-users] SatPulse: server-oriented alternative to gpsd for chrony
- From: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
- Date: Mon, 11 May 2026 10:06:57 +0200
- Cc: chrony-users@xxxxxxxxxxxxxxxxxxxx
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On Fri, May 08, 2026 at 09:15:50AM +0700, James Clark wrote:
> This is very interesting. So the PHC-based refclock_sock output you were
> suggesting for SatPulse would be the same format as ptp4l produces with
> clock_servo as refclock_sock? That would be nicely uniform.
Yes, it should be the same timestamp of the PHC and offset to the
reference.
> I am wondering whether using PHC as the main clock could result in more
> accurate time being served to clients compared to using the system clock as
> the main clock, assuming you had PHC-based refclock_sock input from
> SatPulse, hardware timestamping and no PTM, since you wouldn't have the
> inaccuracy from translating between PHC and system clocks.
The asymmetry between the system clock and the PHC should cancel out
when serving time to clients from the system clock over the same PHC,
so the mean offset shouldn't change, but the stability should improve
significantly. I think that will be the ideal configuration of a
single-interface/PHC NTP server.
--
Miroslav Lichvar
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