Date: Wed, 12 Apr 2000 07:12:05 +1000 From: Greg Black <gjb-freebsd@gba.oz.au> To: FreeBSD-questions@FreeBSD.ORG Subject: Re: Kernel adjustment for clock drift Message-ID: <nospam-38f39525df03b80@maxim.gba.oz.au> In-Reply-To: <nospam-38ec626df002084@maxim.gba.oz.au> of Thu, 06 Apr 2000 20:09:50 %2B1000 References: <nospam-38ec626df002084@maxim.gba.oz.au>
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About a week ago I wrote:
> I've been away from the lists for ages and am looking for an
> update on clock drift management under FreeBSD-3.4R. I have a
> machine that drifts about 7 seconds a day and I'd like to tweak
> something in the kernel to keep it closer to the truth. The
> clock gets corrected once a day by ntpdate, but I'd like to
> avoid such big adjustments.
For the benefit of anybody who wanted to know the answer, I got
the following very helpful response from Poul-Henning Kamp (also
posted on -hackers):
On 3.4 you need to set the frequency of the relevant timecounter.
If you
grep Timecounter /var/run/dmesg.boot
and look at the *last line*, it will say either TSC or i8254.
You can then modify the frequency with the corresponding sysctl
variable:
machdep.i8254_freq: 1193182
or
machdep.tsc_freq: 400911216
and set the frequency there.
Make sure that you have APM firmly disabled in the BIOS.
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