[ntp:questions] How do I validate my PPS clocks?

David Taylor david-taylor at blueyonder.co.uk.invalid
Fri Mar 1 07:26:34 UTC 2013


On 01/03/2013 03:45, ramadog at gmail.com wrote:
[]
> Good call. The manual I have for 1 of my Gigabyte mother boards is useless.
> Managed to find the relevant information. Now have a 3.16GHz core2duo fed with
> a pps. A getnstimeofday() early in the irq code and a 2nd just before the
> normal pps time stamp is taken and still seeing 5us - 6us between the 2 times.
>
> Even with that delay it is still far better than what I get from internet ntp
> servers over my 8160/384 adsl link.

I'm delighted that was of help - the old COM port still lives on!  I see 
something similar in orders of magnitude of behaviour - if not in 
absolute numbers - in terms of syncing.  Of the Internet is worst (Cable 
Modem: 30/3 Mb/s), LAN is better, PPS is best on my Windows systems. 
Much better now with Windows-8 and the precise time call, but still not 
as good as a UNIX-based system.

It will be interesting to see whether others can produce similar time 
differences - on today's GHz processors you can to an awful lot in 5 
microseconds!
-- 
Cheers,
David
Web: http://www.satsignal.eu



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