On Dec 5, 2014, at 5:55 PM, Paul <tik-...@bodosom.net> wrote: [ ... ] >> Even back in 2002 with very inexpensive commodity hardware, FreeBSD was >> able to achieve accuracy measured to ~260 nanoseconds: > > Hmmmm. So phk uses a $1,500 rubidium standard as a system oscillator and > you call it inexpensive and commodity.
No, he used a $1500 rubidium clock to accurately measure the timekeeping quality of a $220 Soekris computer, and concluded: "I have earlier complained that no good and cheap hardware were available which could timestamp a PPS signal reliably and precisely but now the Soekris computer has proven that it does indeed deliver just that: With a pricetag of approx USD220 (single unit including enclosure) this is the best hardware you can find for a stratum 1 NTP server." If you wanted to drive such hardware via a ~$40 GPS puck, you'd probably see an accuracy of around a microsecond, perhaps a bit worse depending on the timekeeping accuracy which the GPS puck provides. That was also the level of accuracy I was seeing from generic Intel hardware running FreeBSD as a stratum 1 with a GPS source. I've used a digital frequency counter which had an onboard TCXO (or possibly a DTCXO) for measuring. Although the frequency counter supported receiving higher-quality PPS timing from an external atomic clock, I've never had a Cs or Rb source, so I won't claim to have measured sub-microsecond accuracy with it. > He also ran a particular install of BSD and a non-standard NTP. I believe he ran FreeBSD 4.x and likely the ntpd from ports. Regards, -- -Chuck _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
