Fan control for PowerMac7_3 (#3)
H. Peter Anvin
hpa at zytor.com
Sun Oct 17 10:58:22 EST 2004
Paul Mackerras wrote:
> H. Peter Anvin writes:
>>It's the backside fan that oscillates; backside_fan_pwm varies between
>>30 and 100 in what is pretty much a squarewave. See attached graph (and
>>note how the other fans vary with workload.)
> The sharp rises look like the code thinks it gets into an
> over-temperature situation and turns the fans on full blast. It could
> be worth putting some printks in the overtemp code.
Changing the unsigned variables to signed per Ben's suggestion seems to
have solved the problem.
>>I probably need to write a "power virus" program for the G5 to really
>>test out the high end (a power virus is a program which keeps the chip
>>running as hard as it can; generally keep all pipelines stuffed.)
> Hmmm, I should see if I can dig such a thing out of somewhere in IBM.
That would be good; otherwise they're not too hard to write given a
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