[ntp:questions] Re: PPS working or not? FreeBSD 5.4

David J Taylor david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk.invalid
Wed Feb 1 10:05:34 UTC 2006


Eugen COCA wrote:
> I have only:
>
> server 127.127.20.1 minpoll 6 maxpoll 6 prefer
> enable monitor stats pps
>
> As I said, I have minor problems with the startup process, as the ntpd
> service need 2 to 8 hours to stabilize to microsecond offset.
>
> And another minor problem: I have two PCs, one with P2/266 - brand
> computer and one AMD k6III/400MHz - "home made" with SOYO motherboard.
> The one with P2 have no problems with temperature variations, as the
> home made one have big problems (offset rising to 100-300 microseconds
> as the temperature changes). I have to study this behaviour too.

OK, Eugen.

I didn't have the "enable pps", and I still don't have it.  Perhaps an ntp 
expert could advise on this?

I'm seeing nearer 10us offset rather than 1us offset:

  http://www.david-taylor.myby.co.uk/mrtg/pixie_ntp.html

but (if I recall correctly) that happens within a minute or two of 
startup.  There was a discussion of some of the issues affecting accuracy 
here:

  http://www.wraith.sf.ca.us/ntp/

For errors as large as 300us, I am unsure as to how that can possibly 
happen with the PPS_SYNC in the kernel.  Perhaps an expert could advise?

David 





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