[ntp:questions] NTP not syncing

Antonio Marcheselli puppa at me.la
Sun Nov 3 01:24:51 UTC 2013

>    That's about it. One of the assumptions made by NTP is that it is running at a fixed clock speed (or rather that the system 'clock source' is). So when that sources frequency is altered for power saving or performance enhancement (you can configure both) , it will be seen as slowing or speeding up  when compared with the configured servers timestamps. If for instance, after booting and ntp startup the cpu goes idle, then the frequency could be lowered, causing the clock source to slow down, causing your problem. In older implementations I believe that the cpu frequency lowering also caused the clock source to slow (ex. the TSC was directly linked to the cpu frequency) but I believe that some newer cpus keep the clock source running at a constant frequency and just modify the execution units frequency to avoid this issue.

Cheers for that, I'll have a look.


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