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

David T. Ashley dta at e3ft.com
Thu Jul 5 20:19:49 UTC 2007

"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!  Consider, also, that they provide no 
> way to adjust the clock hardware.  Computers are designed to compute, not 
> to keep time.  The original IBM PC and PC/XT did not even have a clock; if 
> you wanted a clock it was an add-on at extra cost from a third party.
> 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.

David T. Ashley              (dta at e3ft.com)
http://www.e3ft.com          (Consulting Home Page)
http://www.dtashley.com      (Personal Home Page)
http://gpl.e3ft.com          (GPL Publications and Projects) 

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