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Date:      Thu, 22 Mar 2012 10:51:09 +0100
From:      Alexander Leidinger <Alexander@Leidinger.net>
To:        Luigi Rizzo <rizzo@iet.unipi.it>
Cc:        Matthias Gamsjager <mgamsjager@gmail.com>, freebsd-stable@freebsd.org, John <john@theusgroup.com>
Subject:   Re: powerd and increase in energy need
Message-ID:  <20120322105109.Horde.srohf5jmRSRPavYNP_frKBA@webmail.leidinger.net>
In-Reply-To: <20120321173728.GA41322@onelab2.iet.unipi.it>
References:  <CA%2BD9Qhv5EmrkqvLetx9T5WD_1BRuCpUyZ=VYnRSjwRYqA7phdg@mail.gmail.com> <20120321000058.177F8256@server.theusgroup.com> <CA%2BD9QhsMMXYbLKg__jZx=7KbCHtK6LjqkfL9WSWs=pdT-t9r0w@mail.gmail.com> <CAN6yY1tKYbTjgQsL1gnfrc9r68c%2BQDCb1SAb%2BM=RFA90jvLpnw@mail.gmail.com> <20120321173728.GA41322@onelab2.iet.unipi.it>

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Quoting Luigi Rizzo <rizzo@iet.unipi.it> (from Wed, 21 Mar 2012  
18:37:28 +0100):

> I guess that the credit for power saving goes mostly to the CPU
> architects. Powerd only gives second-order savings, and C1 vs. C3
> is ineffective, at least for HZ=1000
>
>         CPU     Power (watts)
>         freq    idle    16 threads
>         -----------------------
>          200     48      51
>         2200     52      83
>         3200     54     115
>         3401     56     118
>
>         powerd   48     118

I hope you all don't use a cheap PSU, but a _good_ high efficient one,  
which really draws less power when idle instead of generating heat.  
Some PSUs are only efficient in a sweet spot, instead of being  
efficient over a broad range, even when being idle. See  
http://en.wikipedia.org/wiki/80_PLUS for a quick and not so in-deep  
overview (and the reality may differ from manufacturer to manufacturer).

Bye,
Alexander.

-- 
That does not compute.

http://www.Leidinger.net    Alexander @ Leidinger.net: PGP ID = B0063FE7
http://www.FreeBSD.org       netchild @ FreeBSD.org  : PGP ID = 72077137




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