From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wes Felter Subject: Re: How does BIOS "thermal throttling" interact with cpufreq? (on VIA C7) Date: Fri, 15 Jun 2007 11:31:10 -0500 Message-ID: References: <1181856419753@dmwebmail.belize.chezphil.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1181856419753@dmwebmail.belize.chezphil.org> 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=m.gmane.org+glkc-cpufreq=m.gmane.org@lists.linux.org.uk Content-Type: text/plain; charset="us-ascii"; format="flowed" To: cpufreq@lists.linux.org.uk Phil Endecott wrote: > Dear Cpufreq experts, > > I have a Jetway J7F2 motherboard with a VIA C7 processor and have > recently got CPU frequency scaling working with the ondemand governor. > It all works very smoothly - thanks. > > In the BIOS settup screens there are options for "thermal throttling". > They allow me to define a threshold voltage and a "duty cycle"; the > screens are rather vague and there's nothing about it in the board > documentation. My guess is that when the CPU temperature reaches this > threshold the clock speed is reduced. I have looked at the datasheet > for the chip that includes the temperature monitoring logic, and asked > about it on the lm-sensors (aka hwmon) mailing list, and there seems to > be an "over temp" output signal from this chip. (The is also an "alarm" > output, with a separate threshold register, which I think goes to the > speaker.) > > Does anyone know how this stuff works, and how it interacts with > cpufreq? Could it be that the "over temperature" signal is actually > just an interrupt and software is supposed to respond by changing the > frequency? Does cpufreq need to be aware of this throttling function > (i.e. having enabled cpufreq, have I unintentionally disabled this > thermal protection?) If they've done it really right (like Intel TM1/TM2), then the CPU will handle everything transparently for you. If they've done it right, then overtemp will trigger a system management interrupt (SMI) and BIOS code will set the IA32_CLOCK_MODULATION register; because clock modulation is (supposed to be) orthogonal to EIST it should work fine. If they do it some other way then who knows. Wes Felter - wesley@felter.org