From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dag Bakke Subject: Re: cpufreq for older Toshibas with P3-M and ALi chipset? Date: Mon, 03 Jan 2005 00:34:59 +0100 Message-ID: <41D88523.4040809@bakke.com> References: <41D8204F.3090108@bakke.com> <20050102174242.GB15802@dominikbrodowski.de> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20050102174242.GB15802@dominikbrodowski.de> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: cpufreq-bounces@www.linux.org.uk Errors-To: cpufreq-bounces+glkc-cpufreq=gmane.org@www.linux.org.uk Content-Type: text/plain; charset="us-ascii"; format="flowed" To: cpufreq@www.linux.org.uk Cc: ptb@it.uc3m.es Dominik Brodowski wrote: >Hi, > >On Sun, Jan 02, 2005 at 05:24:47PM +0100, Dag Bakke wrote: > > [snip] >>The laptop appears to work with the 'ACPI Processor P-States driver', >>but this only gives me two frequencies to choose between. Is this to be >>expected? >> >> > >Yes, it is. Mobile Pentium 3 CPU only support two frequency scaling states. >The 8 states you're seeing using cpuswitch are throttling states -- i.e. the >CPU is stopped for short periods of time. However, during these periods the >voltag isn't scaled, so it only leads to a linear reduction of power >compared to a ~ ^3 reduction if voltage is reduced as well. Furthermore, the >state the CPU is in when stopped equals the state the CPU is put into when >there is no work to do -- all this leads to the fact that throttling is >useless in most cases. > > I'll test and see how much the drain from the battery changes when using cpuswitch. And compare it with the two P-states. Should have done that anyway. >>None of the cpufreq processor drivers appears to fit the bill for a >>PIII-M on an ALi chipset, >> [snip] >Except the acpi-cpufreq driver, there is none you can use with this system. > > > >>BTW: >>I do notice that if I fiddle with the BIOS settings, I can make the >>laptop boot at "half speed", coming up at 500 MHz instead of 1000. (As >>displayed in /proc/cpuinfo.) And the P-states driver still works, so >>presumably it is possible to combine 'native support' and P-states to >>obtain 16 steps? :-) >> >> > >No :-) Probably this "half speed" mode means the front side bus speed (which >is multiplied inside the CPU) is put to 50%. And unless you find out how >this is accessible during a runtime system, there's no chance to combine >these two. > > > Well, I believe it is just the same function as cpuswitch exploits, because cpuswitch reports the cpu to be running at 'level 4' when I make it boot at 500Mhz. Thank you for a comprehensive answer, even though it didn't come out as positive as I had hoped! Dag B.