Hello All,
I bought a MountainMods ascension duality which supports two motherboards. I have a 2 systems, 1 for work (Linux) and 1 for gaming (Windows). The gaming system is liquid cooled. I'd like to put the work system into my cooling loop.

How can I setup a pump and some fans on a radiator so that they are powered on if either system is powered on? I'd like to set it so that 2 molex devices power on if either power supply 1 or power supply 2 is powered on.

I thought of two options and wondered if the forum folks had better ideas or inputs on these:

Option 1:
Reverse Y-adapter. Instead of taking one molex input and splitting it to two devices, I was going to have 2 molex inputs and one output. I am not too experienced with these things.

Will the voltage change if both PSUs are powered on?

For simple devices like fans and water pumps, is a voltage increase a cause of serious concern? I have a Liang D5 pump that already has a resistor built-in. If I had the pump set to the lowest speed, wouldn't a voltage increase just increase the speed a bit?

Option 2:
3rd PSU with relay. Does anyone know how I can setup a device to power 2 molex devices (my pump and fans) if either PSU is powered on? I've seen such devices for one power supply for AC pumps and have seen something similar in the woodworking world for dust collectors. Does anyone have any idea if something like that exists that can turn itself on if PSU1 or PSU2 is powered on and be smart enough to shut itself down when both are powered off?

Option 3+: Does anyone have better ideas?

Any input is greatly appreciated