From: Dave Jones <davej@redhat.com>
To: Michael Tokarev <mjt@tls.msk.ru>
Cc: Xiaoning Ding <dingxn@ymail.com>, linux-kernel@vger.kernel.org
Subject: Re: a question about p4_clockmod module on Xeon quad core processors
Date: Thu, 29 Jan 2009 12:24:06 -0500 [thread overview]
Message-ID: <20090129172406.GB14096@redhat.com> (raw)
In-Reply-To: <4981A0AC.5030300@msgid.tls.msk.ru>
On Thu, Jan 29, 2009 at 03:27:24PM +0300, Michael Tokarev wrote:
> > p4-clockmod doesn't change the processor frequency.
>
> Hmm.. But what it really does, then?
it modulates the clock so the CPU isn't always availble for doing work.
> I used it one one machine which had a flaky CPU cooler,
> to reduce power consumption during hot summer days.
it reduces the amount of heat generated, by making jobs
take longer to finish. This comes at a cost of the CPU not
being able to enter lower C states for longer periods of time,
so you may end up actually using *more* power.
> It worked, and reportedly the frequency varied from
> 200MHz to the max of 2.4GHz (it's a P4 Xeon).
The CPU was always at 2.4GHz, even if it said '200MHz'.
It was just only doing work once in every 12 clocks.
Dave
--
http://www.codemonkey.org.uk
next prev parent reply other threads:[~2009-01-29 17:24 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-27 20:17 a question about p4_clockmod module on Xeon quad core processors Xiaoning Ding
2009-01-27 21:23 ` Arjan van de Ven
2009-01-29 16:12 ` Xiaoning Ding
2009-01-28 21:02 ` Dave Jones
2009-01-29 2:06 ` Xiaoning Ding
2009-01-29 2:45 ` Dave Jones
2009-01-29 16:32 ` Xiaoning Ding
2009-01-29 17:08 ` Dave Jones
2009-01-29 12:27 ` Michael Tokarev
2009-01-29 17:24 ` Dave Jones [this message]
2009-01-29 19:40 ` Xiaoning Ding
2009-01-29 19:54 ` Dave Jones
2009-01-28 21:05 ` Wes Felter
2009-01-29 2:11 ` Xiaoning Ding
2009-01-29 20:47 ` Wes Felter
2009-01-30 1:12 ` Xiaoning Ding
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