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

ulf.norberg at banverket.se ulf.norberg at banverket.se
Mon Jul 9 06:51:16 UTC 2007


Hi Perry.

Garmin has receiver that gives PPS signal, GPS 18 LVC, and it is quite affordable

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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