[time-nuts] Using a frequency synthesizer replacement for motherboard oscillator

Erich Heine sophacles at gmail.com
Sun Dec 2 19:54:30 UTC 2012


Jonathan,

My research group has had some good experiences using products from Endace (
http://www.endace.com/) for network timing measurement at the ethernet
level. I don't have a pointer immediately to the work, but if there is
interest can ask tomorrow at work. The gist of it though was to understand
precise timing characteristics of network switches for better simulation.
Examining the time "in switch" for various packets at the microsecond level
was needed to understand various delay curves for different network loads,
with an ultimate goal of proper statistical modeling reflecting reality as
close as possible.

I personally have also used endace products to measure packet timings for
research, but I didn't need so much precision for that work - however I can
say they have a good API and decent tech support for interacting with their
cards and products.

HTH.

Regards,
Erich


On Sat, Dec 1, 2012 at 2:35 PM, Jonatan Walck <jwalck at netnod.se> wrote:

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> Eric, your experiences here is of great interest to me too, I've been
> exploring external clocking of Ethernet controllers as of late but
> have not dived into it yet.
>
> I'm more interested in your how, but of course also in your why.
>
> // jwalck
>
> PS. Hey everyone, new to this list since two days joining after
> attending my first PTTI. Working with time and frequency distribution
> in Sweden and with time getting deeper into the field both on and off
> work.
>
> On 12/01/2012 01:15 AM, Eric Garner wrote:
> > I've never done it using to the RTC crystal, but I  do it quite
> > frequently in my Day Job to Ethernet controllers on those same pc
> > mother boards.
> >
> > -Eric
> >
> > On Fri, Nov 30, 2012 at 4:10 PM, Sarah White <kuzetsa at gmail.com>
> > wrote:
> >
> >> On 11/30/2012 6:30 PM, Eric Garner wrote:
> >>> the actual RTC on modern (Intel based) PC's is driven from a
> >>> standard 32,768 Hz crystal attached to the PCH. some of them
> >>> are in incredibly
> >> small
> >>> packages now instead of the old tuning fork-in-a-can ones.
> >>> peeling off
> >> the
> >>> load caps and crystal from the board would allow you plenty of
> >>> spaces to tack down a lead from an external synthesizer.
> >>
> >> Yeah, the one on the (Soekis) example was pretty small. So far
> >> none of of the replies have indicated that anyone on here has
> >> experience beyond an embedded system.
> >>
> >> Mostly I started this thread because there have been a few with
> >> people discussing implementing NTP on embedded microcontrollers,
> >> arduino, etc. and I was thinking of doing it from the other side
> >> (turning a nice-ish server into a rock-solid timekeeper)
> >>
> >> Thanks so far everyone. Really impressed that I already managed
> >> to get 4x replies so quickly :)
> >>
> >>
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