From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aaron Spettl Subject: Re: Centrino: undervolting and further reducing heat Date: Wed, 18 May 2005 15:57:26 +0200 Message-ID: <428B49C6.90505@spettl.de> References: <428B38F2.5080907@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <428B38F2.5080907@gmail.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: cpufreq-bounces@lists.linux.org.uk Errors-To: cpufreq-bounces+glkc-cpufreq=gmane.org@lists.linux.org.uk content-type: text/plain To: cpufreq@lists.linux.org.uk Hi I've got a banias 1.6 GHz processor and like Daniel I've reduced the voltages. My multiplicators and voltages: 6x @ 0.780V (default: 0.988V) 10x @ 0.956V 12x @ 1.004V 14x @ 1.116V 16x @ 1.244V (default: 1.484V) So far I've found nobody who needs higher settings on a banias cpu (I'm admin on a german notebook forum and have seen many values). Dothan cpus need less power, in my experience (very) safe values are: 6x @ 0.732V 10x @ 0.860V 12x @ 0.988V 14x @ 1.052V 16x @ 1.212V 17x (?) 18x (?) As you can see with Daniels cpu (6x @ 0.700V, 16x @ 0.972) these voltages should be no problem for anyone, so I suppose it would be safe to set the default values to these. I think my banias values should be increased by one step (0.016V) to be sure. Idea: Is it possible to set a kernel option like "reduce cpu voltage", maybe even an "aggressive" option? We could leave the original tables for default and activate the lower voltages only if this option is set. A kernel boot parameter could override this option for one session, so people could test it easily. Regards Aaron Nebojsa Trpkovic wrote: >I use undervolted AMD64 on two gentoo boxes for months: > >1. socket 754 nforce3-250gb, athlon64 3000+ (Newcastle core) overclocked >to 2.4GHz and undervolted to run @1.45V > >2. socket 939 nforce4 ultra, athlon64 3000+ (Winchester core) >undervolted to run @1V at 1GHz and @1.275V at 1.8GHz (stable voltages >suficient to run prime95 for hours were 0.9V at 1GHz and 1.175V at >1.8GHz but I like to be 110% safe so I've left extra 0.1V just in case) > >Ofcorse, I had to manualy modify powernow-k8.c > >;) > > > > >Daniel Bonniot wrote: > > =20 > >>Hi, >> >>I have a dothan 1.6 GHz processor, and i've been investigating how to >>reduce heat to minimize fan usage. One very promising avenue is >>undervolting. According to several online articles, there is a large >>potential for undervolting. I ended up modifying speedstep-centrino.c >>to test it out. Results are very positive: it can run under heavy load >>at 1.6Ghz with only 972mV (down from 1340mV). This decreased >>temperature by 10=B0C! At 600MHz, the minimum 700mV was sufficient. >> >>I understand that the driver needs to be conservative by default, but >>given the huge benefits, it would make a lot of sense to offer a way >>to specify lower voltages to those who want to. Has anybody >>investigated this possibility, or already started working on it? What >>would be a good interface to specify the voltages? >> >> >>Independently of this feature, I wonder how it's possible to further >>reduce consumption when the system is mostly ideal, and even 600MHz is >>more than needed. The idea being to let the system cool down even more >>in that case. Is there any existing way to achive this on linux? One >>possibility I found in the intel docs is the IA32_THERM_CONTROL MSR, >>which can reduce clock speed by 12.5% to 87.5%. Am I right in thinking >>that it could be combined with speedstep to achieve even lower power >>consumption states? Are there other possibilities? >> >>Cheers, >> >>Daniel >> >> >>_______________________________________________ >>Cpufreq mailing list >>Cpufreq@lists.linux.org.uk >>http://lists.linux.org.uk/mailman/listinfo/cpufreq >> >> =20 >> > >_______________________________________________ >Cpufreq mailing list >Cpufreq@lists.linux.org.uk >http://lists.linux.org.uk/mailman/listinfo/cpufreq > > =20 >