[ntp:questions] Red Hat vote for chrony
cswiger at mac.com
Sat Dec 6 00:12:20 UTC 2014
On Dec 5, 2014, at 5:55 PM, Paul <tik-tok at 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.
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