New PC build PSU & GPU cable question?

[bryceedmundo]

As the title says, I'm not sure about something. Definitely a noob thing, sorry, first build!

My conundrum:

My power supply (Corsair RM1000x) comes with 2x 8pin to 8pin cables, both labeled CPU. I'm no genius, but I assume these aren't for PCIE devices.
All the 'type 4' PCIE cables that came with the PSU are 8pin to 2x 6+2pin connections... I don't have any 8pin to 8pin connectors other than the one extra labeled 'CPU' and I don't have any 8pin to 1x 6+2 cables, they all have double connectors on the far end.
So...
When my GTX 1070 arrives tomorrow which receives 2x 8pin connectors, am I to plug in TWO of these 8pin to 2x 6+2 cables and leave one of the 6+2s dangling off of each OR will one of these cables with both connectors in the GPU provide enough power to it?

I'm assuming it's just the one cable, being a quality PSU and all.... and if not... that doesn't make any sense.... why are they all Y splitters!?

Thanks for your time!
Bryce

[manikyath]

read trough the manual of your power supply, i was reading trough a seasonic manual the other day, and appareantly they recommend using two cables instead of one cable with two plugs for GPUs above 250 watts, i'm sure corsair has a similar recommendation in their manual somewhere