[ntp:questions] Slightly OT: Looking for good GPS PCI time sources

Thomas Kayser forensic at milwpc.com
Tue Jul 10 07:54:54 UTC 2007

On Mon July 9 2007 01:51, ulf.norberg at banverket.se wrote:
> Hi Perry.
> Garmin has receiver that gives PPS signal, GPS 18 LVC, and it is quite
> affordable

Here's a link to setting up a Garmin 18 LVC for about $80.00USD.


> I don't know if it will give you enough precision, but at the moment my S1
> built on it has an offset within 0.3msec from a Symmetricom NTS-200 in
> Stockholm which is about 250km away.
> Here's a page I made about how to make your own NTP-server with the Garmin
> receiver. http://uffe.hopto.org/linux/ntp/index.html
> At some point I've heard that, to achieve really high precision on
> PC-hardware you either have to run BSD or patch your Linux kernel and then
> add a high precision RTC-hardware (like rubidium or something) to your PC.
> Maybe our NTP-experts here on the mailinglist can verify if thats correct
> or not.
> Regards
> Uffe
> >-----Ursprungligt meddelande-----
> >Från: questions-bounces+ulf.norberg=banverket.se at lists.ntp.org
> >[mailto:questions-bounces+ulf.norberg=banverket.se at lists.ntp.or
> >g] För Perry E. Metzger
> >Skickat: den 6 juli 2007 22:17
> >Till: questions at lists.ntp.isc.org
> >Ämne: [ntp:questions] Slightly OT: Looking for good GPS PCI
> >time sources
> >
> >
> >
> >I'm building a system for a client to measure network
> >latencies in a distributed system very accurately --
> >microsecond accuracy is desired (though I suspect in practice
> >we'll end up doing a bit worse). To do this, I need to get
> >high quality clock sources for the machines doing the
> >measurement. One obvious choice would be PCI cards that
> >synchronize to GPS.
> >
> >I figure if any group has significant experience with such
> >devices, this one would -- anyone have any recommendations?
> >Also, can anyone think of another reasonable way to get this
> >sort of accuracy on stock PC hardware?
> >
> >One consideration might be whether the cards in question allow
> >readout of the time as a single atomic operation -- if they
> >don't, one can't (for example) read the time without worrying
> >about locking...
> >
> >Perry
> >--
> >Perry E. Metzger		perry at piermont.com
> >
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