Hi Rudolf, Forgot to include the attachment. Please check the attachment. Thank you! Yongkui On 10/25/06, Yongkui Han <hanyongkui99 at gmail.com> wrote: > > Hi Rudolf, > > I drew the curve of the fan speed together with the "CPU Temp" and "M/B > Temp" outputs from lm-sensors. The pdf file is attached for your reference. > > The fan speed is very stable before the cpuburn program starts running, > the speed is switching between 3150 RPM and 3323 RPM. > > After the cpubrun program starts running, the fan speed goes up: 3323 RPM > ---> 3413 RPM ---> 3510 RPM ---> 3614 RPM ---> 3723 RPM. And after the > cpuburn program stops running, the fan speed goes down: 3614 RPM ---> 3510 > RPM ---> 3413 RPM. > > Although the fan speed goes up when the CPU temperature is increasing, the > difference of the fan speed is not so much: 3723 RPM vs. 3150 RPM. The > difference is only 573 RPM. Will this difference in the fan speed prevent > the temperature of the silicon chip from increasing rapidly (from tens of > milliseconds to tens of seconds)? > > Do you have any insights about this? > > Thanks! > Yongkui > > > On 10/24/06, Yongkui Han <hanyongkui99 at gmail.com> wrote: > > > > Hi Rudolf, > > > > Thank you for your reply. > > > > On 10/23/06, Rudolf Marek <r.marek at assembler.cz > wrote: > > > > > > Hi Yongkui > > > > > > > I calculated the time constant based on the temperature curve of > > > "CPU > > > > temp". It is about 20 seconds. > > > > > > Ok. Important question: Is the fan switched off - disconnected? I > > > think we see > > > the "slow" start because the system cools down. The board has some > > > kind of > > > automatic cooling. Of course without the fan it might be bit dangerous > > > if system > > > temperature grows, but I think this is necessary to test it ;) Or if > > > you are > > > curious and want to test it ;) > > > > > > Yes, the fan is connected and running all the time. I plan to test it > > without the fan this weekend. I will let you know the new high temperature > > without the fan as soon as possible. > > > > > > > > > > > > In my opinion, the time constant of the silicon chip is about 10 > > > > milliseconds. > > > > > > Well what constant? > > > > > > The thickness of the silicon chip is about 0.5mm, the thermal resistance > > is about R = 0.4 K/W, the thermal capacitance is about C=0.025 J/K, so > > the time constant = R*C = 0.01 second. > > The time constant of the heat sink is about several minutes. > > So it is my expectation that although the temperature of the silicon > > chip changes rapidly, the temperature of the heat sink changes very slowly > > (in minutes). So if the thermal diode is not inside the silicon layer but > > near the heat sink or heat spreader, then the temperature change will be as > > slow as the temperature curve of my experiments (or even slower). > > > > > Does this suggest that the "CPU temp" is not the temperature of the > > > > thermal diode inside the Pentium 4 CPU? > > > > > > Also from the previous mail with graphs, I think it is but system is > > > cooled > > > > > > > Oh, I just thought of one possible reason for this. Perhaps the > > > current > > > > or the voltage drop of thermal diode is not changing so fast as the > > > > temperature change of the silicon area around it. So the temperature > > > > readings from the diode will lag. If this is true, this could > > > explain > > > > why the readings from the thermal diode is not changing as rapidly > > > as > > > > the temperature of the silicon area around it. > > > > > > Yes but not in range of hundreds of seconds. > > > > > > > > > > I am confused here. I still think the "CPU temp" should be the > > > readings > > > > from the thermal diode inside the Pentium 4 CPU chip. But the fact > > > that > > > > this "CPU temp" is changing slowly in seconds and it could not reach > > > a > > > > high temperature makes me doubt it. > > > > > > I think because of that hidden autoregulation. I would suggest to > > > disconnect the > > > fan connector (of course not the heatspreader ;) and try it without > > > that. > > > > > > Will the hidden autoregulation (cpu fan speed change) prevent the > > temperature of the silicon chip from increasing rapidly (from tens of > > milliseconds to tens of seconds)? I have doubt on that. > > Anyway, I plan to try it without fan working to see what will happen. > > > > Sorry for delay, > > > > > > Regards > > > Rudolf > > > > > > > Thank you very much for your ideas on this! > > > > Regards, > > Yongkui > > > > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.lm-sensors.org/pipermail/lm-sensors/attachments/20061025/43125769/attachment.html -------------- next part -------------- A non-text attachment was scrubbed... Name: cpuburn.fan.pdf Type: application/pdf Size: 5454 bytes Desc: not available Url : http://lists.lm-sensors.org/pipermail/lm-sensors/attachments/20061025/43125769/attachment.pdf
