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From: John Baldwin <john@baldwin.cx>
To: freebsd-ppc@freebsd.org
Subject: Re: System clock falls behind quickly on Mac mini G4
Date: Mon, 7 Apr 2014 17:04:58 -0400
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Cc: Alexey Dokuchaev <danfe@nsu.ru>, ppc@freebsd.org
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On Friday, April 04, 2014 6:07:17 pm Justin Hibbits wrote:
> On Fri, Apr 4, 2014 at 7:47 AM, Alexey Dokuchaev <danfe@nsu.ru> wrote:
> > On Sat, Mar 29, 2014 at 05:01:34PM +0700, Alexey Dokuchaev wrote:
> >> On Sat, Mar 29, 2014 at 12:28:12AM -0400, Joe Nosay wrote:
> >> > I'm curious on two things:
> >> > 1. Is ntpd running/set in /etc/rc.conf?
> >>
> >> No, it's off.  I guess if I had it running it won't let the clock to
> >> behave like that. :)
> >
> > Running ntpd(8) unfortunately does not make things better (well maybe it
> > helps a bit, but clock still drifts away pretty fast).  I guess my only
> > option is to run ntpdate(8) periodically. :-(
> >
> > ./danfe
> 
> Curious, could you post your dmesg with boot verbose?  I haven't run
> into a problem with clock drift on any of my ppc machines, albeit I've
> never tested on my mini.  There might be something with your PMU.

Also, if the frequency is calibrated incorrectly during boot for some reason,
your time-of-day clock will drift constantly.  I've seen this on x86 boxes
where the TSC was calibrated incorrectly due to an interaction with SMM
interrupts for legacy USB emulation.  In that case, adjusting machdep.tsc_freq
to match the frequency from the CPU's brand string "fixed" the drift.

-- 
John Baldwin