On wto, 23 mar 2010 12:42:06 in article news:<hoa9di$75a$1@inews.gazeta.pl>
Q wrote:
>> Sterowanie obrotami przez PWM, da się.
>
> osobny kabelek do zasilania "przez pwm"???

Sterowania PWM:

4-Wire PWM Controlled Fans Specification
http://www.formfactors.org/developer/specs/4_Wire_PW
M_Spec.pdf

http://pavouk.org/hw/fan/en_fan4wire.html

Signal Control (PWM) is input for PWM pulses. Base frequency is 25kHz and it
is acceptable from 21kHz to 28kHz. Input has TTL level and includes pull-up
resistor to 5V or to 3.3V in new constructions. Signal is not inverted and
100% PWM means maximal revolutions of fan. Motherboard has open-collector
type output. This construction guarantee, that with disconnected PWM signal
will runs fan with maximum revolutions.