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Date:      Thu, 16 Jul 1998 08:16:45 GMT
From:      jak@cetlink.net (John Kelly)
To:        Bruce Evans <bde@zeta.org.au>
Cc:        current@FreeBSD.ORG
Subject:   Re: tickadj -t not changing tick
Message-ID:  <35adaeab.207380020@mail.cetlink.net>
In-Reply-To: <199807160653.QAA24751@godzilla.zeta.org.au>
References:  <199807160653.QAA24751@godzilla.zeta.org.au>

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On Thu, 16 Jul 1998 16:53:55 +1000, Bruce Evans <bde@zeta.org.au>
wrote:

>>So am I correct in assuming I
>>need to increase the i8254_freq value to match the true oscillator
>>rate, and the kernel will adjust accordingly?
>
>It wouldn't hurt, but I guess you have a Pentium not running SMP or APM, 
>so it wouldn;t help much.

Both 486's and Pentiums, so I need to understand how to tweak both
i8254 and TSC.  One of my 486 machines is fast by 27.68 seconds per
day, so it seems I need to change its i8254_freq to 1,193,564.

>Boot with -v and note the frequency calibrated relative to the RTC and
>use that is input to sysctl, or use CLK_USE_I8254_CALIBRATION to set
>this frequency by default.  The RTC is usually more accurate than the
>i8254.

That's helpful too, but using the value calculated by hand from an
average daily deviation as determined by ntpdate seems more precise,
so I think I'll sysctl my hand-calculated value at bootup somehow.



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