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Re: PPS in GPSD vs Chrony
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From: |
Gary E. Miller |
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Subject: |
Re: PPS in GPSD vs Chrony |
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Date: |
Tue, 30 Jun 2020 11:12:28 -0700 |
Yo Miroslav!
On Tue, 30 Jun 2020 12:39:03 +0200
Miroslav Lichvar <mlichvar@redhat.com> wrote:
> On Tue, Jun 30, 2020 at 12:49:13AM -0700, Gary E. Miller wrote:
> > Miroslav Lichvar <mlichvar@redhat.com> wrote:
> >
> > > For example, I set the PPS on my ublox units to
> > > 32 Hz to get more samples and improve the stability.
> >
> > Interesting. Do you have data on this configuration compared to
> > plain PPS?
>
> No, I can't find any data that would compare a 32Hz PPS to 1Hz PPS
> directly. It's been a while since I experimented with it. The jitter
> of samples updating the clock should roughly improve with a square
> root of the PPS rate.
An ntpviz of different polling rates on several of my hosts showed optimal
poll depends on hardware, and is usually between 2 and 4 seconds. Depending
on whether you are optimings for Frequency offset or Jitter.
If you repear your experiments I'd help you get some data,
RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can't measure it, you can't improve it." - Lord Kelvin
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