[ntp:questions] Is 24PPM an Excessive Real-Time Clock Correction?

Richard B. Gilbert rgilbert88 at comcast.net
Thu Jul 5 20:49:21 UTC 2007

David T. Ashley wrote:
> "Richard B. Gilbert" <rgilbert88 at comcast.net> wrote in message 
> news:468D4A70.9030508 at comcast.net...
>>David T. Ashley wrote:
>>>Any insight into whether 24 PPM is excessive for my server?
>>Consider that a computer manufacturer typically spends something like $2 
>>US on the components for the clock! 

>>24 PPM is pretty good.  Anything up to a hundred or two will usually work 
>>just fine.
> Thanks.  Interesting.  It seems to be a really steady error, i.e. seems to 
> always be between 24 PPM and 24.5 PPM.
> I think I'll write a little software to plot it at a sampling frequency of 
> once per hour.  I'm wondering if it varies by time of day, temperature, etc.

I think you will find that the frequency correction varies with the 
temperature inside the computer case.  A really high quality clock would 
put the quartz crystal inside a tiny "oven" in order to maintain a 
constant temperature and, therefore, a constant frequency.  The computer 
manufacturers won't do it because it wouldn't earn them a cent!

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