Date: Thu, 22 Mar 2012 14:59:46 +0100 From: Luigi Rizzo <rizzo@iet.unipi.it> To: Alexander Leidinger <Alexander@leidinger.net> Cc: Matthias Gamsjager <mgamsjager@gmail.com>, freebsd-stable@freebsd.org, John <john@theusgroup.com> Subject: Re: powerd and increase in energy need Message-ID: <CA%2BhQ2%2BgP3K3xLzhxCoDCZCYL%2BjW5Q4cTT5a5F4GkifmzOsiBKA@mail.gmail.com> In-Reply-To: <20120322105109.Horde.srohf5jmRSRPavYNP_frKBA@webmail.leidinger.net> 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> <20120322105109.Horde.srohf5jmRSRPavYNP_frKBA@webmail.leidinger.net>
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On Thu, Mar 22, 2012 at 10:51 AM, Alexander Leidinger < Alexander@leidinger.net> wrote: > 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 <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 > > -- -----------------------------------------+------------------------------- Prof. Luigi RIZZO, rizzo@iet.unipi.it . Dip. di Ing. dell'Informazione http://www.iet.unipi.it/~luigi/ . Universita` di Pisa TEL +39-050-2211611 . via Diotisalvi 2 Mobile +39-338-6809875 . 56122 PISA (Italy) -----------------------------------------+-------------------------------
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