Question 1

Is it absolutely necessary to connect the "CPU Fan" piece?  Or can I just use this to split my single, solitary case fan header into four more.

Accepted Answer

the big 4 pin molex has to be plugged in because it powers the fans. the motherboard plug doesnt have to be plugged in unless you want to monitor or change fan speed, the fans will go full speed without it. the cpu fan plug is the only plug that is seen by the motherboard ( for speed monitoring). the blue wire is the PWM wire, it controls the fans. the green wire is the speed sensor wire. the yellow and black are 12volt power. standard 3pin fans will plug into the 4pin plugs too. i guess thats all there is to know about this splitter. i been using it for a year now with now problems. hope this helps and have a great day.

Question 2

So since this plugs into the MOBO and the PSU am I safe in assuming this will take the strain of powering the fans off the MOBO so it will live a bit longer? And Will I be able to plug 3 case fans with 3-pin connectors into the fan connectors and control the speeds of all of them through the MOBO? even though the cpu fan connector on this adaptor is a 4-pin, and i would be plugging in a 3-pin case fan into it would that keep this fan from being controlled by the mobo and only limit my fan control to the 2 case fans plugged into the adapters 2 3-pin connectors.

Hope that was clear enough, i know it was a mouthful

Accepted Answer

The answer to your first question is, "Precisely, yes."  Your second question is more complicated; three-pin fans get their fan speed controlled by varying voltage, but PWM fans maintain a constant maximum voltage (and regulate fan speed through the fourth pin).  In other words, your three-pin fans (attached to the three-pin connectors) will all operate at an unvarying maximum speed at all times when split and controlled by a master PWM fan.  Plugging the splitter into a Molex reinforces the constant maximum voltage supply, forcing all three-pin fans to operate at maximum speed.  So, ultimately, when connected to a Molex, this splitter is not designed to control fan speed for three-pin fans at all.  Therefore, your conlusion is incorrect, but yes, I agree that this is clearly a mouthful!

Brand	Rosewill
Model	RCW-FPS-401
Type	Power
Color	Multi-Color

Length	12"
Cable Length	1 ft.

Rosewill RCW-FPS-401 1 ft. PWM Splitter

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Item#: N82E16812119248