I know that i cant connect to mobo header, ill connect with molex. I mean i could keep the high speed all the time, it wouldnt hurt anything, it would just be louder.No. This device is a way to connect several fans using power from a SATA power output from the PSU, and NO power from any mobo fan header. But that means two things are missing. First, there is no way for any fan on this device to send its speed signal to the mobo, so you cannot "see" those speeds. Small point, really. But more importantly, when you connect fans to mobo headers using Splitters, those fans' speeds are controlled automatically by the mobo according to the temperatures measured inside your case. With this device, instead, YOU control the fan speeds by using the small switch on the board, so you have to decide when to change the speeds and do that work.