[ntp:questions] NTPD can take 10 hours to achieve stability

David Lord snews at lordynet.org
Tue Apr 19 14:04:09 UTC 2011

C BlacK wrote:
> I am talking about the cheep crystal oscillator in the local x86 computer.

There are designs for temperature control of the motherboard
xtal and alternative of using an external 14.31818 MHz clock
source. Some of my motherboards even have an external source

I tried an experiment with a watch xtal divided down to give
a pps output with best result drift of only a few ms/day but
worst was more than 1s/day. The module was in the open but
shielded from direct sun.

There is another method where motherboard/xtal temperature is
measured and a correction applied via a patched ntpd.

Sorry but the links I have are no longer working as sites
have moved.


> Chip
> On 04/18/2011 05:54 PM, C BlacK wrote:
>> On 04/17/2011 10:58 PM, C BlacK wrote:
>>> Why would it take ntpd ten hours to achieve its accuracy?  Can this be explained in laymans terms and
>>> mathematically
>>>>> Absolutely normal!  NTPD can sometimes need up to ten hours to achieve 
>>>>> the accuracy it is capable of.
>> Thanks for all the great answers.  Now for a harder question, how does the accuracy of the local clock source
>> affect the accuracy of ntpd.
>> Thanks
>> Chip

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