From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ducrot Bruno Subject: Re: [ACPI] Re: [PATCH 2.6] update passive cooling algorithm Date: Thu, 15 Jan 2004 14:42:29 +0100 Sender: cpufreq-bounces@www.linux.org.uk Message-ID: <20040115134229.GT14031@poupinou.org> References: <20040111211255.GA31105@dominikbrodowski.de> <20040112154611.GH14031@poupinou.org> <20040112173922.GA6154@dominikbrodowski.de> <20040112191122.GK14031@poupinou.org> <20040115121833.GB12963@elf.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20040115121833.GB12963@elf.ucw.cz> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: cpufreq-bounces@www.linux.org.uk To: Pavel Machek Cc: acpi-devel@lists.sourceforge.net, cpufreq@www.linux.org.uk List-Id: linux-acpi@vger.kernel.org On Thu, Jan 15, 2004 at 01:18:33PM +0100, Pavel Machek wrote: > Hi! > > > > > > [Len, could you test and verify this patch, and push it to Linus, please?] > > > > > > > > > > The current algorithm used by Linux ACPI for passive thermal management has > > > > > two shortcomings: > > > > > > > > ... > > > > > > > > > +/* If a passive cooling situation is detected, primarily CPUfreq is used, as it > > > > > + * offers (in most cases) voltage scaling in addition to frequency scaling, and > > > > > + * thus a cubic (instead of linear) reduction of energy. Also, we allow for > > > > > + * _any_ cpufreq driver and not only the acpi-cpufreq driver. > > > > > + */ > > > > > > > > Just a stupid question: > > > > > > > > What is best if processor heat issues (apart turning on the fan)? > > > > > > > > Reducing voltage of the processor, but still allowing it to run execution > > > > at 100% (which is the case if the processor is heating), or reduce > > > > amount of time allowed for the processor to execute? > > > > > > voltage scaling. It offers a much better (quadratic) saving than clock > > > modulation (linear saving). Doing both [and you need to do it, as the CPU > > > won't run with fewer volts at the same frequency] gives you cubic savings. > > > > Yes I know. But does it offer more 'cooling'? > > Of course. > > If you eat less power, you create less heat. CPU is basically fancy > "turn-electricity-into-heat" device. > I don't like certitudes (I was wondering if better heat dissipation in case of throttling even if more heat generation, but that not the case). > [Have you seen that "first use of PentiumPro in house appliances" > picture?] No, but I do have seen some that have burnt in a production server, some years ago... -- Ducrot Bruno -- Which is worse: ignorance or apathy? -- Don't know. Don't care.