Fan control for PowerMac7_3 (#3)
H. Peter Anvin
hpa at zytor.com
Sat Oct 16 15:32:07 EST 2004
Benjamin Herrenschmidt wrote:
> On Sat, 2004-10-16 at 14:58, H. Peter Anvin wrote:
>>I don't know how to tell; it's a significant sound. Let me see if I can
>>figure it out.
> If the dual 2.5Ghz is like the old dual 2Ghz, you can run prefectly well
> with the case open, as long as you keep the plexiglass in place, which
> drives the air flow, and you'll be able to see the CPU and slots fans.
> You can also read the speed values from /sys/devices/temperature
>>OS X doesn't sound like this. The oscillation period for what it's
>>worth is 10 seconds.
> Ok, there must be something wrong then...
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.)
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.)
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