Both 4-pins neccesary?

I'm going to assume you are talking about a 4pin molex to 6 pin PCIe adapter. The short answer is you need to use both pins.

Reason is that if only one was needed they would have set it up that way. But if you use a GPU that needs that much power, the heat from that much current flowing through the wires could melt the insulation off. By using two sets of wires you'll cut the flow of electrons in half, and you don't run this risk. It's probably safe to do so short term, or even long term if you use a GPU that doesn't need a lot of extra power. Like a stock clocked 5750.

Sorry. What I meant was the 4-pin on the mobo by the CPU. There is enough room for 2 of the 4 pins but it will run with just one plugged in.

Ahh, the 12V CPU plug. Same concept applies. You'll have issues if you try OCing your CPU, or if you try to use any of the 125/140W CPUs. (or if you use CF/SLI) If it works you should be ok, just don't push/OC the system.

So having 2 plugged in is a good thing? I'm just trying to figure out which way is better. I have enough plugs on my PSU to have both plugged in. Seems to be running fine with both...... hmmmm why would it run off of one if there is room for 2? Wouldn't you want both?

if you can use both, use them,
I run a mobo with an 8 pin socket but only have a 4pin on my psu and it works fine, but when I upgrade my psu to one with a 4/4 or 8pin, I'll use the 8pins
Moto

Both is better.

Why wouldn't you (if you were a motherboard manufacture) choose to allow only one if possible?

Very true PreferLinux.

Best answer selected by bigtrev85.