Thanks guys!
And how "intelligent" is BIOS pwm (for 4 pin header)?
Well... I know how PWM works -
good read here
But the question is - can it be tricked.
For instance:
with @1500rpm rated fan my mobo bios starts with fan running @900rpm - and that is about 60% of the nominal fan speed. And if I swap the fan for the one rated @800rpm - can PWM be tricked to run it still at 60% speed, a lovely 480rpm?
I'm talking about cold boot when all components have room temperature - so it's not the case of ramping up the fan because of the excessive heat.
I hate when I push the start button and fan starts "screaming" (by SPCR standard) @900rpm - until the system boots and software takes control and slows fans down.
I know every bios and manufacturer makes it different - but generally how this works?
1) PWM just sets the certain fan voltage according (it will be 7V in my case)
2) PWM is increasing the voltage until fan reaches certain rpm (it will be 900rpm in my case)