Hello Nithin: * Jean Delvare <khali at linux-fr.org> [2004-11-22 07:47:54 +0100]: > > In LM93 driver there is no such fan divisors > > present.Is there any other way to solve the problem. > > Oh, you're right. It's quite rare to see fan monitoring chips without > dividers, sorry I missed that. > > > Shall i get fan values by using 3 pin fan.It is > > specified in the data sheet that 4th pin is needed to > > get the fan values while using PWM. > > If the datasheet says you need 4-wire fans, and it doesn't work without > it, then I guess you really need these. I believe these are rather news > since I never heard about nor saw 4-wire fans so far. Sounds like a > smart idea to allow PWM fan speed control while still reliably > monitoring the fan speed (which is hardly the case with 3-wire fans). > > I cannot tell you more as I don't know the LM93 very well, nor do I know > your specific motherboard. I'm the author of the lm93 driver, and I don't understand about the 4-wire fans either. AFAICS the datasheet says no such thing. To clarify about fan tach. vs. PWM: when a fan is driven by low-side drive PWM (which is very common) the tach. signal gets ugly and un-readable especially at low speeds. I don't know how a "4th wire" would correct that. (Although, my degree is CS not EE. When stuff like this comes up I ask an EE coworker.) The lm93 in particular has a "smart fan tach" mode which changes the whole way the "3rd wire" is sampled, and supposedly corrects this problem. The driver supports that mode; please read the available documentation for how to enable it. I have no idea if this mode works or how well. But, if you're not using it already, try it. I would be interested to know if that fixes the problem for you. Regards, -- Mark M. Hoffman mhoffman at lightlink.com
