Subject: Re: A proposal for Time Synchronisation in NetBSD
To: Jan-Simon Pendry <>
From: None <>
List: tech-kern
Date: 12/17/1993 21:56:06
jsp> if you need a system call to set/get the rtc why not
jsp> use getitimer/setitimer with a new interval timer,
jsp> say ITIMER_RTC?

Yes, that's one of the more attractive solutions to the out-of-kernel
syncing, but I'm still thinking about that one.

It would lean towards a pair of operations, one to read the RTC (good),
and one to set it.  Unfortunately (as outlined below) I believe we
need to be able to set the softclock directly.  Where we need to set the
RTC, setting the softclock as well is ok, but not vice versa (have I
missed something?).

jsp> i'm not sure i understand why it is necessary to set the
jsp> softclock without setting the rtc, after all you are going
jsp> to be setting them to the save value - no?  in that case
jsp> settimeofday would do just fine.

Reading from the RTC and then writing that value back to the RTC
(which the resettodr in settimeofday would do) introduces an error into
the RTC.  On many architectures the RTC only resolves to the nearest

- David B.