[ntp:questions] Using different timebase for ntpd

Greg Dowd GDowd at symmetricom.com
Mon Mar 23 18:37:12 UTC 2009

The normal method, and the cleanest, is to provide a reference clock
driver and let ntp keep the kernel clock synchronized to the card
timebase.  If you are bound and determined to make your own code, the
place to start is in configure to specify your clock model and then
systime.c in libntp.  Be advised that you are not likely to get much
support for modifications to that file as a great deal of knowledge is
required to understand the control loop and which variables you can or
should tinker to match your hardware.

-----Original Message-----
From: questions-bounces+gdowd=symmetricom.com at lists.ntp.org
[mailto:questions-bounces+gdowd=symmetricom.com at lists.ntp.org] On Behalf
Of Patrick Loschmidt
Sent: Monday, March 23, 2009 8:27 AM
To: questions at lists.ntp.org
Subject: [ntp:questions] Using different timebase for ntpd


I'm trying to replace the linux/unix system clock by a special clock
maintained on a PCI card. The clock can be set, rate adjusted, etc., so
I have the equivalent for gettimeofday(), settimeofday(), adjtime(),

Unfortunately, I'm confused by the number of different abstraction
levels within the NTP package. I first started replacing the functions
in libntp/systime.c (get_systime, adj_systime, set_systime). Then I
found out, that there are direct calls to adjtime() from within ntpd.
Further I see some ntp_adjtime() calls.

Can anybody enlighten me, where would be the best place to use a
different timebase for ntpd, or do I have to go trough all the


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