GTX 770 2x8-pin connectors, only 1 PCI-E slot on PSU

woijo · Jul 20, 2014

Hey,

I just finished a gaming grade mini-ITX build using a Silverstone ST45SF Gold rated PSU: http://www.silverstonetek.com/product.php?pid=342&area=en

The problem is that I'm using a Gigabyte GTX 770 rev 2.0 which needs two 8-pin power connections, while my PSU only has one 8-pin PCI-E out.

At first I used a standard PCI-E cable which split into one 8-pin and one 6-pin, but it wouldn't start up, saying the card wasn't connected to the PSU properly.

I switched out the cable to a PCI-E 8-pin to 8-pin for the first slot on the GTX and then used one of the 8-pin to double-molex adapters which came with the card for the second slot, and ran that into a random empty 6-pin PSU socket.

So at the moment, my card is getting half of it's power from the PCI-E and the other half from a spare connection on the PSU.

This most likely isn't ideal, but it seems to run fine for the time being. Tested everything in Futuremark's Flame Strike and ended up with a 7449 score, which seemed decent for a small form factor build.

My question is, should I be worried about this Frankensteinian power setup for my GTX? What would be the best solution here?

The rest of my build for details: http://pcpartpicker.com/p/rJ2BGX

ksham · Jul 20, 2014

It isn't ideal, but you can power the graphics card via molex to PCIe adapters. So you should be fine.

toyftw · Jul 20, 2014

woijo :

Hi - Just be aware that 600w/42 +12v amps is what's recommended for that GPU/sys. Given
that, you are underpowered.

However, the gtx770 pwr req's are the same as the gtx780, but it does require less. You
can run the sys with 34 +12v amps. You have 37 +12v amps. The issue I see is you have a "k"
processor, meaning you intend to OC. I don't believe 3 +12v amps is enough headroom to OC.

If you are going to OC, you need more power.

thelasthallow · Jul 20, 2014

your power supply is way under powered for that GPU anyways. you would have ben better off getting a 760 or a 750Ti with that low of wattage and amperage. i bet that in a few months your PSU will die simply because it cant keep up with the total power draw from your whole system. especially if you intend to overclock or add more fans/HDD's

woijo · Jul 20, 2014

toyftw :

Hey, thanks for the quick replies. My build was inspired by the Falcon North-West Tiki, which should be able to run anything up to a titan with similar components and the SIlverstone 450 SFX PSU. As much as I've gathered, GPU manufacturers tend to note down higher requirements to protect users against low quality PSUs. However, that Silverstone one should be of high build quality and more than enough to power everything fine.

I don't particularly intend to OC the other components, due to the small size of my case and no actual internal airflow.

I checked the manuals for the PSU and now know that I'm powering the seconds 8-pin slot on the GTX through a 8-pin to double molex male, continued into double molex female, which runs into a IDE/SATA 6-pin slot on the PSU, to clarify my situation.

Strangely enough, the 8-pin to double molex male cables which came with the card, only have 6 actual connection pins where it connects to the card's 8 pin slot. The molex ends are corresponding, both with 3 pins. So I guess it should be fine to leave it running like it is, into the PSU's 6-pin IDE/SATA slot.

toyftw · Jul 20, 2014

woijo :

Hi again - Yes, GPU mfgs overstate wattage req's for the reasons you mention. Which is why I explained
your sys could run on 34 +12v amps and not the 42 that NVidia lists. However, as long as you realize
the PSU has 37 +12v amps and act accordingly, you can run the sys (withoput OC) as I said above.

guru 3d isn't a mfg or seller & here is their take:

Here is Guru3D's power supply recommendation:

GeForce GTX 770 - On your average system the card requires you to have a 550 Watt power supply unit.
GeForce GTX 770 2-way SLI - On your average system the cards require you to have a 750 Watt power supply unit as minimum.
GeForce GTX 770 3-way SLI - On your average system the cards require you to have a 1000 Watt power supply unit as minimum.
If you are going to overclock your GPU or processor, then we do recommend you purchase something with some more stamina.

woijo · Jul 20, 2014

Hm, when you say "act accordingly" you mean keeping the speeds on the other components at stock? I'm a complete novice in builds, other than the research I did on the Tiki and other RVZ01/ML07 builds before selecting the parts.

So I'm still unsure here if my current power setup for my GTX, half coming from the PCI-E slot and half from a random IDE/SATA slot is advised?

Thank you for the quick feedback so far.

toyftw · Jul 20, 2014

woijo :

Ah, I meant don't OC CPU or GPU. That PSU includes 1 6pin + 1 6+2pin pcie connectors. You should
be fine using a 6 pin to 8 pin adapter for the other connection.
http://www.newegg.com/Product/Product.aspx?Item=N82E16812119483&cm_re=6_pin_to_8_pin-_-12-119-483-_-Product

woijo · Jul 20, 2014

Thanks for all the help, I'll need to order a 6-pin to 8-pin adapter then, couldn't find one when I searched my nearby shops on Friday, so I went with this less-than-great temporary solution for now.

Hopefully I'll be able to switch up to the 650W SFX, that Silverstone just released, sometime soon. That should give me more room for longevity.

toyftw · Jul 20, 2014

woijo :

Ah, I linked an adapter above only $4, someone close to you prob has one tho. If not, order from Newegg or Amazon & you'll have it in a few days.

Altho this might be more suitable:
http://www.newegg.com/Product/Product.aspx?Item=N82E16812200420&cm_re=6_pin_to_8_pin-_-12-200-420-_-Product

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