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Date:      Thu, 16 Jul 1998 18:53:34 +1000
From:      Bruce Evans <bde@zeta.org.au>
To:        jak@cetlink.net, phk@critter.freebsd.dk
Cc:        bde@zeta.org.au, current@FreeBSD.ORG
Subject:   Re: tickadj -t not changing tick
Message-ID:  <199807160853.SAA31913@godzilla.zeta.org.au>

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>>You want to fiddle kern.timecounter.frequency (units: Hz) or
>>kern.timecounter.adjustment (Units: PPM/2^16)
>
>Judging from what Bruce said, it seems that kern.timecounter.frequency
>is derived from the machdep.*_freq variables, so it would be better to
>change them and let the kernel propagate the changes.

It would be nicest to change the machine-independent variables and let
the kernel propagate the changes to the machine-dependent variables and
hardware.  However the kernel makes no attempt to propagate the changes.
OTOH, when you change the m-d variables, the kernel attempts to propagate
the changes, but it doesn't succeed (it sets the active frequency,
possibly causing a glitch due to the non-atomic update, and the change
gets blown away at the next clock interrupt).

>And if the appropriate machdep.*_freq variable is set precisely, is
>there any need for kern.timecounter.adjustment?

Only in practice.

Bruce

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