PCI-E on Seasonic Platinum 860 and EVGA 1080 FTW

[radiomir]

I've got a Seasonic Platinum SS-860XP (1st version), which comes with 2 pcie cables that have 12 pins on one end and 2 x 6+2 on the other.

I just got a new EVGA GTX 1080 FTW that requires 2 x 8 pin and have no idea whether I need to use one or both of the above described cables (if I use both, each cable would have one of the 6+2 pin heads on one end dangling.

I am confused because Seasonic recommends this:

not this:

But, I think this recommendation assumes that the power supply has 8 pin pcie connections. Any suggestions?

 

[Barty1884]

You want to use the 6 portion of each "6+2" connector. The 2's will 'dangle' there.

All those diagrams are trying to show is to use two individual cables (one for each 6pin).

 

[radiomir]

You want to use the 6 portion of each "6+2" connector. The 2's will 'dangle' there.

All those diagrams are trying to show is to use two individual cables (one for each 6pin).

Actually, the FTW requires two 8 pin connectors - not 6 pin - so on the gpu side of things I will definitely need to use all four of the 6+2 ends . Perhaps my description wasn't very good, but the pcie cables that came with this particular psu have a 12 pin on one end (which connect to one of the four 12 pin pcie slots on the psu), and on the other end are two 6 + 2 ends. So for the 1080 FTW gpu (which takes 2 8 pins) there are enough ends to plug in to the gpu with a single cable. But, because there is only a 12 pin at the psu side of things, I don't know if that single pcie cable is enough to actually support two 8 pin connections.

The PSU is a modular design and has plenty of amps coming from the 12V rail (71), and plenty of wattage, so it could be okay, but I want to be absolutely sure before I start powering a $600 gpu in this way.

Alternatively, I could use two of the above described cables, but only use one set of 6+2 ends for each. But, that means that 6 of the individual wires coming from each of the 12 pins on the psu side of things would not be connected to anything, so I don't know if this would make a difference - that is, I don't know if using 12 pins from a single pcie connection on the psu is equivalent to using half of the pins (6) on two of the psu's 4 pcie connections.

Make sense?

 

[radiomir]

For anyone that finds this:

I spoke on the phone with a rep from EVGA (very good service as always), and was told that one cable should be sufficient based on how Seasonic does its wiring, the amps from the 12v rail (which he knew without me telling him), and the FTW's power requirements.

I then got an email response from Seasonic, which basically reiterated the above diagram suggesting two cables for cards that require more than 225 W in load.

The FTW has a max power draw of 215W, so based on this and the discussion with EVGA, I imagine I will be fine with a single cable, which has a 12 pin conector at the psu end and then splits to two 6+2 pins that are all plugged into the gpu.