GTX 770 and PSU question

[cmdub]

So 1 or 2 simple questions, I finished my build a week or so ago and runs great but was looking to get some better insight in regards to my PSU and GTX 770 and how they work together. I have the Antec tp-650c and a 2gb evga GTX 770. I know that the 770 requires min 42A on the 12V rail yata yata. My question is more along the lines of how the +12V rail works on most modern PSUs. On mine the manual seems to imply that the +12V2 is solely for the pci-e connections (2 seperate cables) and +12V1 is for everything else essentially. Theres 30A between them but are they shared? Second question is how I should be hooking up my video card in relation to the PSU, is using 1 single cable enough as shown here

or should I be using the 2nd PCI-e cable for the bottom 6 pin slot, does it matter either way?

I haven't run into any issues yet as the video card seems to be running fine while gaming but was looking for some clarification on these mainly cause I'm curious and couldn't find the answer through googling

 

[Suztera]

It doesn't matter either way. With the current setup in your picture, it is fine.

 

[Dark Lord of Tech]

If your POWER SUPPLY features 2 - 12v rails , then it would better to use 2 PCIE cables so that the rails will share the load.

 

[ksham]

To start off, I'm going to start listing some specs.

According to nvidia, the GTX 770 requires two PCIe power connectors -- one 8-pin and one 6-pin. It has a TDP of 230W and nvidia recommends a PSU of at least 600W.

The Antec TP-650 is 650W PSU with two 6-pin supplementary PCIe power connectors and two (6+2)-pin supplementary PCIe power connectors.

So off the bat, the PSU satisfies the recommended wattage. You need to use one (6+2)-pin and one 6-pin to power the GTX 770. With that taken care of, we'll look at the +12V requirement. The PSU has two +12V rails, each capped at 30A and a total current rating of 54A. The GTX 770 requires a minimum of 20A on the +12V rail. So clearly, no issues there. The PSU is more than sufficient to power the GTX 770.

When nvidia said 42A, they meant 42A for the entire system not the card itself. 42A may not be correct in your case, it's is just a recommendation nvidia set forth.

 

[Scampi]

If you look at the power distribution charts in these reviews for the 750W model. The 12V1 rail gives power for the sata cables etc... & the 12V2 rail is for the PCI-E power connectors.

http://www.techpowerup.com/reviews/Antec/TP-750C/2.html
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story2&reid=382

The 42 Amps requirement for GTX 770 is with the entire system, not just the card, and that number is the system overclocked & in full stress in something like Furmark, which is more stressful than real peak gaming.

Edit: infact 42 Amps is a bit high in general, compared to the 30 Amps requirement of the GTX 760:

GTX 770
System Wattage with GPU in FULL Stress = 304 Watt/25 Amps
Subjective obtained GPU power consumption = ~ 195 Watt/16 Amps
http://www.guru3d.com/articles_pages/geforce_gtx_770_review,5.html

GTX 760
System Wattage with GPU in FULL Stress = 280W/23 Amps
Subjective obtained GPU power consumption = ~ 169 Watts/14 Amps
http://www.guru3d.com/articles_pages/geforce_gtx_760_review,5.html

 

[Pondering]

Use the 2nd PCI-e cable for the bottom 6 pin slot since it uses 2 +12V rails.