On Mar 18, 07:28, David J Taylor wrote: > Not far more constant, no. On the FreeBSD/Pentium-133 system over the > last 72 hours the frequncy varied between about -0.6ppm to +0.4ppm from > the mean, and on the Windows XP system from about -1.4ppm to +1.1ppm from > the mean. So about 1ppm variation as opposed to 2.5ppm, about 40% of the > frequency variation. > > As far as I can tell, the NTP offset is more a function of the control > loop parameters than of the actual hardware (with ~150us offsets and yet > only 2.5us jitter).
The 150us offsets are while slewing to try to catch up with the 3ppm frequency shift as the heat comes on. I have to imagine a Windows PC with a more stable oscillator (lower temperature coefficient to frequency) would do better, though I'm not deluding myself that it would match the performance of FreeBSD, with its advantage of knowing the precise relationship between the counter and the system clock. > There is another issue - version numbers. The FreeBSD runs 4.2.0-a from > May 2005, the Windows 4.2.4.p6 from 2009. I don't know whether there may > have been internal changes affecting the offset compared to the jitter. I have no familiarity with 4.2.0 but keep in mind it's even older than 2005, that's the FreeBSD release date and they were not keeping up wth NTPv4 builds very closely then. From my perspective comparing its performance to the new Windows stuff, it would be awfully nice to get 4.2.4p6 on your FreeBSD box. There are plenty of helpful FreeBSD wizards hanging around here who could help with any issues you have building the reference implementation and installing it in place of the system-provided one on that FreeBSD box. At least I think they would, but given your treacherous discussion of moving away from FreeBSD in favor of Windows maybe you'd get the cold shoulder ;) > I have checked for a temperature monitoring SNMP plug-in, but not found a > compatible one as yet. SNMP is ideal, but anything that could read a temperature that had a high degree of correlation with your osciallator's crystal temperature would be enough to build upon. I'm afraid anything built in to your hardware (like CPU core temp) is not well-enough correlated the crystal temp. Cheers, Dave Hart _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
