Can you use 6 pin power plugs in 8 pin GPU?

[OnionRings]

My friend just bought a GTX 1080 and it has 2 8 pin power sockets but his PSU only has 2 6 pins, can he still use the 1080 until he upgrades his PSU? Obviously, he can't overclock it, but will it stay stable? The big questions though is it won't damage the card or anything? I don't have the answer for him as I always check my PSU before an upgrade, but he forgot to and all the stores near him are closed so he can't get one tonight.

[ARikozuM]

The two extra pins are for grounds. He can use the two 6-pins by buying an adapter for "6-pin to 8-pin".

[OnionRings]

Just now, ARikozuM said:

The two extra pins are for grounds. He can use the two 6-pins by buying an adapter for "6-pin to 8-pin".

Ok so definitely don't do it since those are the grounds, it means that if a surge happened it could fry his card?

[DocSwag]

He can buy an adapter, but if his psu doesn't have 8 pins he might want to upgrade it since it might not be good quality, what psu is it?

[ARikozuM]

Just now, OnionRings said:

Ok so definitely don't do it since those are the grounds, it means that if a surge happened it could fry his card?

The two grounds help the 8-pin deliver an additional 75W over the 6-pin. 

[MimigaKing]

3 minutes ago, OnionRings said:

My friend just bought a GTX 1080 and it has 2 8 pin power sockets but his PSU only has 2 6 pins, can he still use the 1080 until he upgrades his PSU? Obviously, he can't overclock it, but will it stay stable? The big questions though is it won't damage the card or anything? I don't have the answer for him as I always check my PSU before an upgrade, but he forgot to and all the stores near him are closed so he can't get one tonight.

he could also get this two molex to 8pin. 

 

[OnionRings]

Just now, DocSwag said:

He can buy an adapter, but if his psu doesn't have 8 pins he might want to upgrade it since it might not be good quality, what psu is it?

Ok he just checked he has an adapter but one 1, it takes 2 6s and makes it an 8, is 1 8 pin enough to power the card?

[DocSwag]

Just now, OnionRings said:

Ok he just checked he has an adapter but one 1, it takes 2 6s and makes it an 8, is 1 8 pin enough to power the card?

My question is what psu does he have?

[OnionRings]

1 minute ago, DocSwag said:

My question is what psu does he have?

Its a poopy pre built dell psu its only 450w

[DocSwag]

Just now, OnionRings said:

Its a poopy pre built dell psu its only 450w

He might want to consider upgrading it. A Seasonic S12ii is only $45 and much better quality.

[OnionRings]

Just now, DocSwag said:

He might want to consider upgrading it. A Seasonic S12ii is only $45 and much better quality.

Of course, as I said he wants to, but everything is closed tonight, and will be closed tomorrow because of easter, so in the mean time will 1 8 pin be enough power? Or does he have to wait until monday?

[DrMikeNZ]

Just now, OnionRings said:

Of course, as I said he wants to, but everything is closed tonight, and will be closed tomorrow because of easter, so in the mean time will 1 8 pin be enough power? Or does he have to wait until monday?

Wait.

[DocSwag]

Just now, OnionRings said:

Of course, as I said he wants to, but everything is closed tonight, and will be closed tomorrow because of easter, so in the mean time will 1 8 pin be enough power? Or does he have to wait until monday?

Most likely the GPU won't work with only 1 power connector plugged in, but you could always try I guess. Shouldn't do any harm.

[OnionRings]

Just now, DocSwag said:

Most likely the GPU won't work with only 1 power connector plugged in, but you could always try I guess. Shouldn't do any harm.

Alright. He's calling micro center before they close to see if they are open tomorrow, google says they might be, I know some stores don't close for holidays.

[DeadlyMuffinCat]

1 minute ago, OnionRings said:

Of course, as I said he wants to, but everything is closed tonight, and will be closed tomorrow because of easter, so in the mean time will 1 8 pin be enough power? Or does he have to wait until monday?

Honestly just wait until monday, not sure if the card would even power on with just 1 power connector.  

 

[DocSwag]

2 minutes ago, OnionRings said:

Alright. He's calling micro center before they close to see if they are open tomorrow, google says they might be, I know some stores don't close for holidays.

Damn he lucky he lives near a micro center lol for me it's a 1 hr drive  

[OnionRings]

2 minutes ago, DeadlyMuffinCat said:

Honestly just wait until monday, not sure if the card would even power on with just 1 power connector.  

 

 

He's gonna try, it probably won't though. I understand his impatience though, he's been gaming on a GT 730 for so long moving up to a 1080 is a huge increase, he's excited to destroy them frames.

[OnionRings]

Just now, DocSwag said:

Damn he lucky he lives near a micro center lol for me it's a 1 hr drive  

2 1/2 for me, over the Bay Bridge.

[Enderman]

6 minutes ago, OnionRings said:

Its a poopy pre built dell psu its only 450w

Then don't use adapters, because it's definitely not high enough quality or power to run an 8 pin GPU like a 1080.

Unless you enjoy house fires.

Buy a new PSU.

 

[DocSwag]

9 minutes ago, Enderman said:

Then don't use adapters, because it's definitely not high enough quality or power to run an 8 pin GPU like a 1080.

Unless you enjoy house fires.

Buy a new PSU.

 

Ooo me I enjoy house fires!

[mariushm]

6pin connectors have 3 voltage wires and 3 ground wires.

8pin connectors have 2 additional ground wires. The extra ground wires are there only to tell the video card that the connector is different. 

 

According to the PCI-E standard, a video card should not pull more than 75w through a 6pin pci-e connector. If the video card detects those two additional ground wires, it's allowed to pull up to 150 watts through that 8pin pci-e connector.

 

Physically, the connector contacts are capable of transferring up to around 10A of current (per contact) to the mating connector. The wires themselves can carry up to 8-10A per pair of wires - AWG16 wires can do up to around 12A, AWG18 (most common) can do around 10A and AWG20 (more common in cheaper 300-450w power supplies) can do around 6A per pair of wires.

So basically, with the most common AWG18 wires, a video card can receive through a 6pin or 8pin pci-e connector up to 3 pairs x 8A per pair x 12v = 24 x 12 = ~ 280 watts.

The guys that made the standards specified the 6pin connector to 75 watts, because they had to think about super cheap power supplies that may use only AWG 20 wires, and that maybe the cheap chinese manufacturer may use a crappy connector that heats more when a lot of current flows through it, or there may be a poor connection between some of the contacts. 

So basically, a 6 pin connector must only be able to do 75 watts, or around 2A per pair of wires, around 1 fourth of the maximum capability of the connector.

 

A 8 pin connector tells the video card that it may take up to 150 watts through that connector. Power supply manufacturers are supposed to use at least AWG18 rated cables and you'd have 50 watts per pair of wires or around 4A per pair, which is around 40-50% of the maximum recommended current for the wires and connectors. So there's still some room for safety and everything.

 

Your 450 watts has two 6 pin pci-e connectors, probably on a single strand, and probably using AWG18 cables.  That means that the whole strand coming from the power supply is physically capable of transferring up to around 250-280 watts of power safely but if that much power can actually be delivered by the power supply is another thing. If it's a single rail design, yes, the power supply could deliver that much. If it's dual rail, the power supply may restrict this to around 200-250 watts - by using two 6 pin connectors, the power supply manufacturer only guarantees it can give at least 2 x 75w =150 watts through those connectors.

 

A GTX 1080 may have 2 x 8 pin connectors, but that doesn't mean the video card will use up to 2 x 150 watts or 300 watts. In reality, the video card will use up to around 160 watts, maybe a bit more... let's say 180 watts. Furthermore, around 20-40 watts of those 180 watts are taken from the pci-e slot and not from the pci-e 8 pin connectors, so in real world, the video card will only take around 150 watts through those 2 x 8 pin connectors

The manufacturer could have used a single 8 pin connector but they probably wanted the video card to be able to take a bit more than 150 watts, in case user wants to do overclocking. So they had the option to add a 6 pin connector and raise the maximum power to 60w from slot + 150w from 8 pin connector + 75w from 6 pin connector, but it would look ugly to have a mismatch of connectors, so they just went with 2 x 8 pin connectors. 

So because the card will actually take only around 60-80 watts through each of those 8 pin connectors, if you're not going to overclock the card, it should be perfectly fine to use a couple of those 6pin to 8 pin adapters to power the card until you get a better power supply.

 

Note that a 450w power supply typically can output around 300-350 watts on 12v. Higher end power supplies that use DC-DC converters to produce the 5v and 3.3v from 12 as needed typically can produce 420-440w on 12v out of those 450 watts - if the video card uses up to 180 watts and the cpu probably uses around 60-100 watts when it's working hard, that leaves you little room for other things. You should at least NOT overclock the cpu and the video card with such a low power video card.

 

 

[rcald2000]

OnionRings Please correct me if I'm wrong, but your friend has zero options in this situation.  Your friend has a PSU with two 6 pin connectors.  The graphics card requires two 8 pin connectors.  1 of 2 of the 8 pin PCIe adapter will require the only two 6 pin PCIe connectors available.  The GTX 1080 will not power up with only one of it's two connectors plugged in.  Do not even consider daisy-chaining molex adapters -> to -> 6-to-8 pin adapters -> to the GTX 1080.

 

Also, while I'm a fan of the Seasonic S12II 520, it's inappropriate for a dual 8 pin GTX 1080.  The power supply below would be a great choice.

 

EVGA G2 650

104.99 ($89.99 After Rebate)

http://www.microcenter.com/product/457337/SuperNOVA_G2_650_Watt_80_Gold_Modular_ATX_12V_Power_Supply

 

[mariushm]

@rcald2000 , GTX 1080 cards don't even reach 200 watts of power consumption, from both pci-e connectors and the slot.

See http://www.tomshardware.com/reviews/nvidia-geforce-gtx-1080-pascal,4572-10.html

 - 133 watts average from pci-e connectors and 40 watts average from slot, so about 170w average power consumption. It peaks up to 270w from pci-e connectors for milliseconds at a time, which is normal and every card does it, and power supplies are designed for that so you can ignore that higher number.

. 

They use two 8 pin connectors simply to allow overclockers to push cards above those 200w average power consumption. Even with auto overclocking made by the video card, it won't go above around 200 watts... barely a bit more than the limit of a single 8 pin connector.

 

[rcald2000]

mariushm I believe that you misunderstood my point.  If his friend attempts to connect his specific GTX 1080 with only one 8 pin PCIe connector he will receive the error " please power down and connect the PCIe power cable(s) for this graphics card".

 

The second PCIe connector for that card is not optional.

 

FYI: Respectfully, the Tom's Hardware review that you cited is for a reference (aka founders) card.  It's not relevant to your argument.

 

[OnionRings]

Ok guys so he's gonna get a new PSU tomorrow but he wants to know if the 1080 will even work on this board he has http://www.ebay.com/itm/Dell-XPS-8900-DDR4-LGA1151-Intel-Desktop-Motherboard-XJ8C4-AS-IS-/302279257862?_trksid=p2385738.m2548.l4275