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To: Alexander Leidinger <Alexander@Leidinger.net>
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Fri, 28 Oct 2005 15:34:57 +0200."
	<20051028153457.d0wqgn2ask4sgw4k@netchild.homeip.net> 
Date: Fri, 28 Oct 2005 16:21:16 +0200
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Cc: current@freebsd.org
Subject: Re: TSC instead of ACPI: powerd doesn't work anymore (to be
	expected?) 
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In message <20051028153457.d0wqgn2ask4sgw4k@netchild.homeip.net>, Alexander Lei
dinger writes:

>> In general, if you run powerd to change your cpu clock (= TSC
>> frequency), using TSC as timecounter is _not_ what you want to do.
>
>Is it not possible to recalibrate on frequency change, or is it "just" that
>nobody wrote the code do to it?

It's all a matter of what precision you want and how sensitive you
are to jumps.

Making it work in one specific (well chosen) machine is possible,
making it work in general across all possible types of PC hardware
is not.

>We need to document this in the powerd man-page and let powerd tell the user
>if he tries to run in this unsupported mode. Any volunteers (I'm moving my
>PC's to the new appartment at the weekend, so I can't volunteer)?

Our defaults do the right thing I belive.  It's only when the user
overrides the defaults that bad things happen.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.