[ntp:questions] NTP + PPS on Atom motherboards

David Taylor david-taylor at blueyonder.co.uk.invalid
Wed Aug 1 10:17:45 UTC 2012

On 01/08/2012 09:46, Hahn, Ron wrote:
> Colleagues,
> I have been working for some time now trying to get four different Asus Atom motherboards to successfully work as a NTP stratum 1 server.  I am using the FreeBSD 8.3 OS with PPS compilation in the kernel, and the ntp-devel port (4.2.7p2?? version ntp).  Thanks to the David Taylor web site, I am using the Sure GPS boards to drive these motherboards and also his MRTG script to monitor these things too.
> What I am seeing is that the time is off by almost 53,000uS on the MRTG graph and almost 500mS sometimes on the outputs of ntpq -c pe at times.  Other times it is a few uS from PPS.  I have been seeing this on three different boards (D525, D510, and 330 CPU) so this is repeating.  I was thinking this might be the tty port so I have tried both the tty ports and still the same.
> I have used exactly the same recipe on a Core 2 Duo Tyan server and the times are maximally off by only +4uS/-2uS from PPS.  So I am thinking there is something fundamental wrong with the Atom boards.  I have repeated the experiments with a Pentium 4 server in another location and I am also seeing excellent timekeeping too.  I am thinking that maybe the Atom clock on the board is too consumer for these uses??
> Has others experienced these difficulties with Atom motherboards as Stratum 1 servers?
> Thanks,
> Ron

This is the performance I see from an Intel Atom system:


about as good as I would expect.  The motherboard in that PC is an Intel 
D410PT.  So I think that the problem is not from using an Intel Atom per 
se.  I also have an ASrock Intel system which is LAN-synced, and the 
offsets there are a few milliseconds, but not 53 ms.
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