The motherboard I'm getting (ASRock z77 extreme 4) has 3 chassis fan headers. The fans I'm going to be using are 12V each for max rpm. Via the motherboard software, the chassis fan speeds can be automatically controlled based on the CPU temp. I'd like to know if I can get 5 chassis fans into 3 headers with Y cables or something. I know that I can’t exceed the total output voltage of each chassis fan header, so theoretically the minimum output I'd need per header would need to be 24V. I don't own the motherboard yet so I don't have a manual that specifies the voltage outputs of each header on the board, and I couldn't find them online either. What I could do is have 3/5 of my fans automatically controlled via the software, and the remaining 2 connected to the PSU with a fan controller. CPU_FAN1 and CPU_FAN2 will both occupied, and there is another header called PWR_FAN. But to my knowledge plugging a fan into PWR_FAN will run the fan at max rpm and not be controllable. I don't want to turn knobs all the time, so is there an alternate method? Maybe supply the power for the fans directly from the psu, but use the header pins to control it?
Also one of the CPU fan headers has 4 pins and the other one has 3. Will this mean one of my PWM fans’ speed won’t adjust to the speed of the other? This is a push pull setup, and to my understanding a PWM fan needs 4 pins to be controlled.
I plugged a y-cable into a Zotac mini itx to run an 80mm led and a 70mm and had no problems. I think you don't theoretically need 24v per header, you need more amps. It seems to reason if you don't have enough power to run both fans at full speed then they will never spin up to their maximum potential. if you power a fan from the psu then when the machine goes to sleep or standby those fans will continue to run and suck dust into your box.
I've got one set up like that and it's a pain when I want to standby. But it's a bigger pain to clean out the box.