[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!





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