Fan control for PowerMac7_3 (#3)
H. Peter Anvin
hpa at zytor.com
Sat Oct 16 14:58:07 EST 2004
Benjamin Herrenschmidt wrote:
> On Sat, 2004-10-16 at 14:24, H. Peter Anvin wrote:
>>Benjamin Herrenschmidt wrote:
>>>Ok, here's a new patch that fixes a few issues, it's been
>>>tested on a non-liquid cooled system and appear to work ok.
>>I'm testing it out right now. It is definitely suffering from some
>>degree of oscillation when idling, and it seems to be one particular
>>(set of) fan(s) that is having that problem.
> Which ones ? The CPU fans ?
I don't know how to tell; it's a significant sound. Let me see if I can
figure it out.
>>Note that one cause of oscillation at low speed is that there is a
>>minimum speed below which the fans will simply stop. This may be what
>>is happening here.
> Do the fan actually stop ? Yes we "floor" the fan speeds and indeed,
> Apple algorithm is known to slowly oscillate, on my box it's between
> 300 and 1000 RPM for the CPU fans over a period of a minute or 2.
> Such an oscillation is expected. Something worse would mean we get
> something wrong. Did you compare against OS X ?
OS X doesn't sound like this. The oscillation period for what it's
worth is 10 seconds.
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