[ntp:questions] Installing more stable oscillator?
Richard B. Gilbert
rgilbert88 at comcast.net
Fri Jul 13 14:30:58 UTC 2007
Pete Stephenson wrote:
> After a few days of running with good sync to internet servers, my test
> server's system clock shows a drift of about -27ppm, which seems to be
> pretty reasonable for a cheap crystal oscillator.
> However, I occasionally see people in this newsgroup discussing various
> alternative oscillators, like oven-stabilized crystals, rubidium and
> cesium frequency standards, and even hydrogen masers.
> Obviously, many of these options are far too large to simply replace the
> computer's hardware oscillators. How, then, are these oscillators used
> with NTP servers?
They are not used as simple oscillators. They are used as an entire
clock. A clock is basically an oscillator to provide "ticks" combined
with a device to count the ticks.
So, you add the "clock option" and interface the clock to your computer.
> Is it possible to have NTP completely ignore the computer's crystal
> oscillator and use an external oscillator? For example, can one have a
> GPS reference clock sending the time and a PPS signal to discipline an
> external rubidium oscillator (or oven-stabilized crystal, or cesium, or
> whatever), which is then used to supply time to other systems via NTP?
Possibly by rewriting NTP! Ntpd interfaces with the system clock and
disciplines it. Poul Henning Kamp (PHK) has built computers with a
rubidium oscillator for a timebase and disciplined the clock with ntpd
and a GPS reference. These are NOT general purpose computers, they are
high tech clocks!
More information about the questions