[ntp:questions] Re: disciplining two clocks with the same ntpd?
dave-gnus at bfnet.com
Fri Jan 23 18:16:40 UTC 2004
Piotr> You should discipline your system (software) clock with NTP,
Piotr> then store the time into RTC once every few minutes (default 11
Piotr> under Linux with PPSkit).
I know that's what I *should* do. But here's my problem:
1) The RTC clock is more accurate than the system clock
2) This is an embedded system where there may or may not be access to
3) I need to configure all systems the same whether they have full,
spurios, or no access to the Internet
So I figure I could slave the system clock to the RTC as the default,
and then if the access is available, that will discipline the RTC.
If I were to try, as you suggest, to discipline the system clock by
the in-accessible Internet, then write the system clock to the RTC,
then I would have the not-very-accurate system clock disciplining the
more-accurate RTC, which I want to avoid!
Piotr> Please note, that any get/set time on RTC clock (x86):
Piotr> a) wont give you more than 1-seond accuracy,
...which doesn't seem to be a problem for me. I only need my clocks
to be acurate to +-1 second or so.
Piotr> b) will have too huge jitter to make it useful.
...I don't understand, how does the jitter make it useless?
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