From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bas Mevissen Subject: Re: Which cpufreq driver is best for ... Date: Thu, 04 Sep 2003 14:36:45 +0200 Sender: cpufreq-bounces@www.linux.org.uk Message-ID: <3F5731DD.8050700@basmevissen.nl> References: <20030903055749.GA21721@gamma.logic.tuwien.ac.at> <20030903192749.GA30360@brodo.de> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20030903192749.GA30360@brodo.de> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: cpufreq-bounces@www.linux.org.uk Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Dominik Brodowski Cc: cpufreq@www.linux.org.uk Dominik Brodowski wrote: > > No, speedstep-ich is "superior". p4-clockmod only "throttles" the CPU, i.e. > it scales down the frequency but not the voltage. This results in an > approximately linear saving of energy. I think the confusion about clockmod workings (and hence the savings that can be gained from it) comes from the fact that "mod" in clockmod is misinterpreted as "modification" (but it stands for modulation). > And as long as ACPI C-States "idling" or APM "hlt" instructions work, the > CPU is "throttled"[*] if there is no work to do anyway, so the p4-clockmod > driver doesn't save you anything. The p4-clockmod driver almost only is > useful where ACPI or APM "idling" is borken. > Maybe this (together with your extensive explanation in this thread) can be FAQ-ed. With a good explanation of the power saving models (clock modulation, clock modification&voltage scaling, cpu idling) a lot of questions can be answered. Regards, Bas.