Hi Paul: * Paul Crowley <paul at lshift.net> [2006-06-28 13:13:40 +0100]: > Mark M. Hoffman wrote: > > I skimmed through the blog entry and the earlier one which it references. > > In your first attempt you reinvented the 'P' part of a PID control loop. > > Don't give up! ;) There's a *ton* of info about PID controllers on the > > web. If you're still interested, you could start here: > > > > http://en.wikipedia.org/wiki/PID_controller > > Very interesting stuff, thanks! > > My quick reading of this stuff indicates a possible problem. On my > system at least, I can only read the temperature in whole degrees; > lm-sensors returns a number in thousandths of a degree, but sadly the > last three digits are always zero. This means that our differentiation > of the temperature will be very crude, which could make it difficult to > build a functioning PID controller. Read under 'Limitations' in the wikipedia article. One suggestion is to just skip the differential band altogether (PI controller). > How can I find out the maximum safe operating temperature of my current > CPU? Since my first priority is something that works on my current > system, the only reason for me to pick this up again and explore in more > detail is if I can afford to slow the fan even when the system is flat > out, which means I need to know how fast I can run it. You can find this info in processor datasheets, which are available on Intel/AMD websites. It shouldn't be too hard to find. Otherwise, you could consider 55 C to be a very conservative limit. Some Intel cpus are OK up to 85 C, but it really does depend on the model *and* maybe even the stepping. Something else to consider: if you do tune your system to keep the CPU near max temp, make sure that the extra heat is not going to affect your disk(s). Regards, -- Mark M. Hoffman mhoffman at lightlink.com
