M
mc
- Jan 1, 1970
- 0
I did some experimenting. On a 3-wire CPU fan, yellow is power (+12V or
less, down to about 8 V for slow speed), black is ground, and green is sense
(open collector to ground, square wave, one cycle per revolution, so 90 Hz =
5400 rpm = full speed).
The supply voltage is adjusted by the motherboard on the basis of the
measured CPU temperature, which should be between 40 and 50 C.
If the temperature stays below 40 C, you can experiment with putting 1N4001s
in series with the yellow lead so that the default speed will be lower.
People are marketing "quiet fan cables" that do this.
Quality of the heat sink grease between the CPU and the heat sink is
critical. I now know from personal experience that the silver-powder grease
sold in computer stores is MUCH more conductive than ordinary white
heat-sink grease.
less, down to about 8 V for slow speed), black is ground, and green is sense
(open collector to ground, square wave, one cycle per revolution, so 90 Hz =
5400 rpm = full speed).
The supply voltage is adjusted by the motherboard on the basis of the
measured CPU temperature, which should be between 40 and 50 C.
If the temperature stays below 40 C, you can experiment with putting 1N4001s
in series with the yellow lead so that the default speed will be lower.
People are marketing "quiet fan cables" that do this.
Quality of the heat sink grease between the CPU and the heat sink is
critical. I now know from personal experience that the silver-powder grease
sold in computer stores is MUCH more conductive than ordinary white
heat-sink grease.