Emiliano Pastorino wrote: > > There is a way to check the temperature under Linux. It involves > the "lmsensors" package, but I don't know the exact details. > > > Yes, that's what I've been using. The package is lm_sensors, if > installed, you just have to type "sensors" and you get the temperature > in ºC. > > I've already checked that temperature never goes beyond 100ºC, so it > is working. > > But how does it work? Is it just underclocking?
The CPU changes the clock ratio dynamically when the temperature gets too high. > I've checked /proc/cpuinfo, but clock is always at ~1GHz > I don't know the details of how /proc/cpuinfo gets the clock information. You can see the clock transitions in Open Firmware as follows: ok 198 .msr show-temperature (cr many In the unthrottled case, the MSR value will be 04060a06.04000a06. In the throttled case it will be 04060a06.040c0406. The fields in that value are AABBCCDD.EEFFGGHH, where AA is the lowest supported clock ratio BB is the lowest supported voltage CC is the highest supported clock ratio DD is the highest supported voltage EE is the lowest configured clock ratio FF contains status bits GG is the current clock ratio HH is the current voltage All of the voltage fields are 06, which means that the voltage doesn't change. The minimum clock ratio is 04, meaning 400 MHz, the maximum is 0a (decimal 10) meaning 1 GHz. The GG field is normally 0a - full speed - but changes to 04 briefly when the processor throttles back to drop the temperature from 100 to 95. The FF status field changes from 00 to 0c when throttling is in process. It is possible that /proc/cpuinfo is reporting the correct information, but the throttling happens too briefly to notice the change. The CPU runs at full speed until the temperature reaches 100, then it drops back to 400 MHz, but very quickly resumes full speed operation when the temperature drops to 95. _______________________________________________ Devel mailing list [email protected] http://lists.laptop.org/listinfo/devel
