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6-pin to 8-pin adapter VS. 2 molex to 8-pin adapter

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February 13, 2014 7:59:01 AM

What should i use I have a Gigabyte GTX 770 4GB that uses 2 8-pin connectors but i only have one 8 pin and one 6 pin. Should i use the 2 molex to 8-pin adapter or should i buy a 6-pin to 8-pin adapter?

Thanks for your help.
February 13, 2014 8:02:50 AM

I'd avoid using molex to power graphics cards.
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February 13, 2014 8:07:31 AM

Or where can i find another Pcie modular connector for 8-pin for my PSU? model is thermaltake black widow 850w W0319RU.

PS: the card came with 2 of the 2 molex to 8-pin connectors.

EDIT: also i guess my PSU has 2 6-pins and a 8-pin so maybe i should get a 2 6-pin to 8-pin adapter?
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February 13, 2014 8:13:15 AM

You can use just one of the molex to 8-pin to satisfy the second 8-pin plug. Should work without a problem. It's not an absolute must to use only PCIe cables.
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February 13, 2014 8:14:04 AM

Acually i can't find a 2x 6-pin to 8-pin adapter....any suggestions I NEED IT ASAP.

But so i would plug both molex connectors in to power the 8 pin? because its 2 molex connectors to one 8 pin.
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February 13, 2014 8:25:18 AM

You can still use your GPU in the meantime. Just don't overclock it much, the 2x8pin connection isn't REQUIRED to run it, 770s come stock with 1x8pin & 1x6pin connectors. The 2x8pins are simply to provide more power when overclocking on your particular model.
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February 13, 2014 9:14:44 AM

huilun02 said:
You can use just one of the molex to 8-pin to satisfy the second 8-pin plug. Should work without a problem. It's not an absolute must to use only PCIe cables.


I agree.
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February 13, 2014 9:42:51 AM

Alright thanks for all you help guys ill use the molex to 8-pin. I won't be overclocking at all anyways.
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February 13, 2014 5:06:14 PM

If you aren't going to be overclocking, then don't bother with the adapter. Like I said, just run it with an 8pin and a 6pin.
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February 14, 2014 4:37:13 AM

doubletake said:
If you aren't going to be overclocking, then don't bother with the adapter. Like I said, just run it with an 8pin and a 6pin.


No way in heck would I do this. There are two 8-pin adapters for a reason. Don't even give your card a chance to be underpowered. Just do what huilun02 has suggested. There's nothing wrong with power adapters. This is why the manufacturers include them in the box.
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February 14, 2014 5:43:50 AM

The only reason the second 8pin is there is to provide more power than usual. Most of the time, on air, you won't even be able to overclock a card high enough for that extra power supply to make a difference. One thing that lots of people have done yet probably don't even remember is flashing a 6950 to a 6970. For most people, this ran flawlessly, even though a flashed 6950 has 1x8 + 1x6 and a real 6970 has 2x8. I've also tried this out with my GTX 660Tis, an MSI model that had 1x8 + 1x6, and a Galaxy model that has 2x8. It made 0 difference in overclock ability and/or stability to use only a 6 pin instead of a second 8 pin. Do you honestly think that any 770, even with double the VRAM, NEEDS 2x8 when even a stock 780 doesn't?

But w/e, don't try things for yourself to figure them out, just go on conjecture.
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February 14, 2014 5:56:57 AM

Well looking at the specs on newegg for my PSU i guess it comes with 2 8-pins i guess i over looked that option ill have to dig my PSU box out with the extra cables and check it out. Says it comes with 2 6pin and 2 8pin....
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February 14, 2014 6:42:11 AM

doubletake said:
The only reason the second 8pin is there is to provide more power than usual. Most of the time, on air, you won't even be able to overclock a card high enough for that extra power supply to make a difference. One thing that lots of people have done yet probably don't even remember is flashing a 6950 to a 6970. For most people, this ran flawlessly, even though a flashed 6950 has 1x8 + 1x6 and a real 6970 has 2x8. I've also tried this out with my GTX 660Tis, an MSI model that had 1x8 + 1x6, and a Galaxy model that has 2x8. It made 0 difference in overclock ability and/or stability to use only a 6 pin instead of a second 8 pin. Do you honestly think that any 770, even with double the VRAM, NEEDS 2x8 when even a stock 780 doesn't?

But w/e, don't try things for yourself to figure them out, just go on conjecture.


I know what you're saying. A single 8-pin plus the PCIe slot power would be enough to power just about any 770 (225W total between the 2), but do we know how the power is distributed once it gets to the card? Does the card just add the total of all inputs and distribute it that way or does it take some from this input for this part of the functionality and some from this input to power this functionality. I don't know. What I do know is there are Electrical Engineers smarter than I am when it comes to this and usually they don't design products to be produced with extraneous parts (ie extra power inputs) because it takes away from the bottom line.
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February 14, 2014 8:09:13 AM

ubercake said:
they don't design products to be produced with extraneous parts (ie extra power inputs) because it takes away from the bottom line.


They do when it's a high-end, high-margin model marketed for its ability to be pushed past stock performance levels :\
If I'm wrong, why is it that Asus, PNY, Gigabyte and Zotac make their 4GB cards with only 1x8 1x6 layout and not 2x8?

OP probably has an EVGA or MSI card. They probably add the second 8pin as a checkmark feature so people think they'll overclock better.
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February 14, 2014 8:16:01 AM

doubletake said:
ubercake said:
they don't design products to be produced with extraneous parts (ie extra power inputs) because it takes away from the bottom line.


They do when it's a high-end, high-margin model marketed for its ability to be pushed past stock performance levels :\
If I'm wrong, why is it that Asus, PNY, Gigabyte and Zotac make their 4GB cards with only 1x8 1x6 layout and not 2x8?

OP probably has an EVGA or MSI card. They probably add the second 8pin as a checkmark feature so people think they'll overclock better.


Well if your looking at the pictures on newegg to determine they are 1 6 and 1 8 don't bother i thought this card was 1 6 and 1 8 because thats what the picture shows(the specs didn't tell) and it shows 1 6 and 1 8 and when i got the card it has 2 8....
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February 14, 2014 8:18:00 AM

doubletake said:
ubercake said:
they don't design products to be produced with extraneous parts (ie extra power inputs) because it takes away from the bottom line.


They do when it's a high-end, high-margin model marketed for its ability to be pushed past stock performance levels :\
If I'm wrong, why is it that Asus, PNY, Gigabyte and Zotac make their 4GB cards with only 1x8 1x6 layout and not 2x8?

OP probably has an EVGA or MSI card. They probably add the second 8pin as a checkmark feature so people think they'll overclock better.


So the second 8-pin is just to trick people? Makes sense.
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Best solution

February 14, 2014 8:30:22 AM

The 8-pin PCIe connector has 2 additional ground (neutral) pins vs the 6-pin. It does NOT have additional +12V wires. The additional grounds lower the total CONNECTOR resistance and allow more power transfer, but in reality a 8-pin does not have twice the capacity of a 6-pin (which the 150 watt vs. 75 watt rating would imply).

Two molex to one 8-pin is a better solution than 6-pin to 8-pin, since each molex can handle 2 ground circuits. The molex connector is rated for 8 amps per pin on standard 18 ga. wire, so 2 connectors (2x +12V and 4x ground, total) can handle more than 192 watts on the +12V and 384 watts on the ground circuits.

If the card has 2x 8-pin connectors, you MUST connect 2x 8-pin power sources. The PCIe slot and a single 8-pin are not rated to supply the max stock TDP power of the GTX 770.
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February 14, 2014 8:36:22 AM

ubercake said:
So the second 8-pin is just to trick people? Makes sense.


The second 8-pin connector provides more stable power (less voltage droop), and allows the card to be designed to exceed 300 watts, which a 8+6 is not rated for.
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February 14, 2014 8:41:01 AM

This has to do with the power distribution I alluded to earlier. Are you in electrical engineering by chance?
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February 14, 2014 8:42:14 AM

BlacKHawK3 said:
ubercake said:
So the second 8-pin is just to trick people? Makes sense.


The second 8-pin connector provides more stable power (less voltage droop), and allows the card to be designed to exceed 300 watts, which a 8+6 is not rated for.


I was kidding when I said that previous sentence makes sense. Everything you have to say really does make sense.

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February 14, 2014 8:45:38 AM

ubercake said:
BlacKHawK3 said:
ubercake said:
So the second 8-pin is just to trick people? Makes sense.


The second 8-pin connector provides more stable power (less voltage droop), and allows the card to be designed to exceed 300 watts, which a 8+6 is not rated for.


I was kidding when I said that previous sentence makes sense. Everything you have to say really does make sense.



I know, but your sarcasm probably isn't obvious to most people here :D 

I'm actually a mechanical engineer, but I have a lot of experience with electromechanical system design.
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February 14, 2014 8:45:51 AM

ubercake said:
This has to do with the power distribution I alluded to earlier. Are you in electrical engineering by chance?


No but he did stay in a holiday inn express last night :D  LOL

Anyways thanks for all your guys help alot to take in! If i can't find the other 8-pin connector i am going to go with the 2molex to 8-pin adapter.
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February 14, 2014 8:51:06 AM

BlacKHawK3 said:
ubercake said:
BlacKHawK3 said:
ubercake said:
So the second 8-pin is just to trick people? Makes sense.


The second 8-pin connector provides more stable power (less voltage droop), and allows the card to be designed to exceed 300 watts, which a 8+6 is not rated for.


I was kidding when I said that previous sentence makes sense. Everything you have to say really does make sense.



I know, but your sarcasm probably isn't obvious to most people here :D 

I'm actually a mechanical engineer, but I have a lot of experience with electromechanical system design.


I'm really glad people like you are on the forums. I was about to go unplug half the power cables in my system if you wouldn't have commented. kidding ;) 

Seriously though, you provided some good info. Thanks.
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February 17, 2014 12:41:25 PM

GOOD NEWS FOLKS! So as i said i might have 2 8-pins with my PSU well i found the other rocking 2 6+2 pin connectors and rocking 60 fps bf4....frag on!
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February 18, 2014 4:25:39 AM

That's great! That game is a blast.
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February 18, 2014 5:47:40 AM

You know it! I was a COD fan boy until i got bf4, now i can't imagine the reason i even played COD....COD sux compared to BF4!!
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February 18, 2014 6:03:37 AM

I like both for single-player. Multi-player there's just no comparison; BF4 all the way.
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!