CPU Fan/CPU Opt - both need to be connected

[The Boke]

Hi all,

I have an Asus ROG Maximus VII Ranger motherboard and a Corsair H80i GT cooler. Everything is working fine but I have a question about connecting to the fan headers.

The instructions to the H80iGT say that I have to connect the pump power cable to the CPU_FAN header on the motherboard and connect the fans that are attached to the radiator to the two connectors coming off the pump. This I have done.

However, if I don't connect anything to the CPU_OPT header I get a CPU FAN error when booting. If I connect the cooler to the CPU_OPT header instead of the CPU_FAN I get the same error.

I have to have something connected to both of the headers. To get over this I have connected a case fan to the empty header.

Everything is working fine, the machine is rock solid and the fans only spin up when the machine is under load. I'm getting a CPU temp of 34c when the machine is idle and I've not seen it go above 65c-ish when under load.

I don't see it as a problem but I'm just curious, why do I have to have both headers connected?

Thanks

 

[The Boke]

Thanks for the reply. I've done a little bit of trial and error and have noticed that when I un-installed Corsair Link I was able to have the cooler plugged into the CPU_HEADER and leave the CPU_OPT empty. When I re-installed Corsair Link I had to have both headers connected.

I have HWMonitor installed, what should I be looking at for CPU temperatures?
Under the ASUS heading I have TZ00, TZ101, Mainboard and CPU
Under Intel i7 4770 I have Core #0 to #3 and Package

If the temperatures are running too high, could it be that I haven't sat the cooler on the CPU properly, is it worth re-sitting it?

I'm also running FurMark to do a CPU burner test in order to put the CPU under load.