powerd and increase in energy need

[Luigi Rizzo]

On Thu, Mar 22, 2012 at 10:51 AM, Alexander Leidinger <
Alexander at leidinger.net> wrote:

> Quoting Luigi Rizzo <rizzo at 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 <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).
>

it isn't such a big deal in my opinion. The %efficiency at low
levels is misleading if you don't factor out the 5-10W plateau for keeping
the
PSU alive (fan, ballast, etc.). See for instance

http://www.techpowerup.com/reviews/Antec/HCG-520/5.html

the table at the end of the page reports 6.73W of idle power. At 40W
this PSU consumes 52.9W, so the apparent efficiency is 75%, but
factoring out the idle power you go way up.

cheers
luigi

-- 
> 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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