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Date: Mon, 10 Jun 1996 19:18:12 -0600
From: Nate Williams <nate@sri.MT.net>
Message-Id: <199606110118.TAA11261@rocky.sri.MT.net>
To: Bruce Evans <bde@zeta.org.au>
Cc: nate@sri.MT.net, current@freebsd.org
Subject: Re: CLOCK stuff at bootup
In-Reply-To: <199606110018.KAA02186@godzilla.zeta.org.au>
References: <199606110018.KAA02186@godzilla.zeta.org.au>
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> >> Because defining one or both might work better.  Using sysctl to set the
> >> actual (current) value might work better still.
> 
> >Umm, what am I supposed to set using sysctl?  I don't remember ever
> >seeing this kind of detail in old email.
> 
> Clock nominal frequencies.
> 
> >> The i8254 clock determines long term accuracy.  Run for a while and
> >> determine the drift and/or the time daemon adjustments.
> 
> >How?
> 
> Compare the output of `date` with an accurate clock or look in the time
> deaemon log files.

And how would I do that?  I'm not sure what kind of 'drift' I'm
expecting.

(Forgive me, but I'm not clock expert, nor do I understand what all of
this buys me if I have to hand-set all of these variables.)

If I have to hand-set everything and play with this on a per-machine
basis, then it's not worth it.  What does having all of this flexibility
buy me?

> >> Use sysctl to
> >> specify the i8254 clock frequency that minimizes the drift and/or the
> 
> >How?
> 
> Look in the output of `sysctl -a` to find the relevant variable and set
> it as usual.

machdep.i8254_freq: 1193182

This was set at bootup time already, so how do I determine what to set
it to except via trial and error.

> 
> >> The i586 clock determines intra-clock-interrupt times.  Specify the i586
> >> clock frequency that minimizes the jitter in getttimeofday().
> 
> >How?
> 
> First find the frequency.  Set it as above.

machdep.i586_freq: 0

Set it to the stuff that was kicked out by the kernel?  Why isn't aren't
these values already set by default?


Nate