Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753616AbZDELpM (ORCPT ); Sun, 5 Apr 2009 07:45:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752018AbZDELo4 (ORCPT ); Sun, 5 Apr 2009 07:44:56 -0400 Received: from chili.geekmind.org ([78.46.44.80]:51391 "EHLO chili.geekmind.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751363AbZDELoz (ORCPT ); Sun, 5 Apr 2009 07:44:55 -0400 X-Greylist: delayed 501 seconds by postgrey-1.27 at vger.kernel.org; Sun, 05 Apr 2009 07:44:55 EDT Message-ID: <49D89884.2000308@chown.ath.cx> Date: Sun, 05 Apr 2009 13:39:48 +0200 From: Grigori Goronzy User-Agent: Thunderbird 2.0.0.18 (X11/20081125) MIME-Version: 1.0 To: Matthew Garrett CC: Corentin Chary , Cristiano Prisciandaro , Thomas Renninger , Dave Jones , acpi4asus-user@lists.sourceforge.net, linux-kernel@vger.kernel.org, cpufreq@vger.kernel.org, Tom Hughes , linux acpi , Francesco Lattanzio Subject: Re: [Acpi4asus-user] [PATCH 1/1] cpufreq: eeepc 900 frequency scaling driver References: <1227454026.7262.59.camel@localhost> <492A7632.4040106@compton.nu> <200811241613.25557.trenn@suse.de> <200811241736.53067.trenn@suse.de> <1227567739.6421.44.camel@localhost> <71cd59b00904050043u44d1cd2eu4b8d3aee9027ea17@mail.gmail.com> <20090405102057.GA14089@srcf.ucam.org> In-Reply-To: <20090405102057.GA14089@srcf.ucam.org> X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1513 Lines: 32 Matthew Garrett wrote: > I don't think there's a terribly good reason to use the SHE methods if > the CPU supports speedstep. 945 will automatically drop the frontside > bus in the deepest P states. I'd be surprised if it gave any real world > benefits on the atom based systems. > It does make quite a difference, especially because the chipset and CPU are undervolted in the "powersave" preset. Also, SHE offers a slight overclock (with the "performance" preset) which cannot be achieved with mere multiplier switching. This is all guaranteed to be safe by Asus. On my Eee PC 901, the idle power consumption drops from about 7W to 5.8W when switching from "normal" to "powersave". That's about 15%. Under load the benefit seems to be even greater. I'm the author of a program called eee-control, which currently uses another method to change FSB and voltage. It directly communicates with the PLL controller over SMBus and with the embedded controller through some I/O ports. This method works, but is not very safe and very hardware specific. The ACPI interface of Asus' SHE abstracts all the hardware differences away and thus would be preferred. Anyway, my point is: my experience and reports by users show that the difference is *huge*. Regards, Grigori -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/