# PCIe 6pin, 8pin - differences



## PLSBX (Jul 2, 2016)

Hello,

I looked at PCIe 6 pin and 8 pin connectors specification.

6pin can deliver only 75w when 8 pin 150w.

Physical differences - two more ground pins.
How it works? Did anybody test it?


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## R-T-B (Jul 2, 2016)

PLSBX said:


> How it works? Did anybody test it?



It works because the 6pin is actually severely underrated and only lacks a bit of stability at around 150w, which the ground connectors tend to fix (at least, IIRC).

And yes, that's their tested output.  No one really needs to test as it's been tested several times by numerous users and standards groups over the years.


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## PLSBX (Jul 2, 2016)

R-T-B said:


> only lacks a bit of stability at around 150w


So 6 pin should provide 100-120 watt of stable power?

Are additional ground cables only for power stability?


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## Jetster (Jul 2, 2016)

Just goes to show the importance of a proper ground

And it rated for 75 and 150. Not only can deliver


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## newtekie1 (Jul 2, 2016)

PLSBX said:


> Physical differences - two more ground pins.
> How it works? Did anybody test it?



The technical spec difference is actually 2 more ground pins(one used as a sense pin) and an extra +12v pin.

The 6-pin, according to the official spec, only uses 5 of the 6 pins.  3 ground pins, and the two outer 12v pins are used, the center 12v pin is listed as "no connection".

Here is the pin-out chart:


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## PLSBX (Jul 2, 2016)

I looked at some low-end PSU and every 6pin PCIe has 3 of 12v cables.


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## newtekie1 (Jul 2, 2016)

PLSBX said:


> I looked at some low-end PSU and every 6pin PCIe has 3 of 12v cables.



Most do, but back when the 6-pin connector was first becoming popular a lot didn't.  Most today are 6+2 connectors, so they have the 3rd 12v so it can be used with both.


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## PLSBX (Jul 2, 2016)

I found a modecom feel III (Wow, it is still working ) with PCI 6pin (not 6+2) and it is 3x12v.


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## newtekie1 (Jul 3, 2016)

PLSBX said:


> I found a modecom feel III (Wow, it is still working ) with PCI 6pin (not 6+2) and it is 3x12v.



You're point?


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## PLSBX (Jul 3, 2016)

Almost.. one more question.

Is 6pin rated for 2x 12v, right?


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## P4-630 (Jul 3, 2016)

PLSBX said:


> I found a modecom feel III (Wow, it is still working ) with PCI 6pin (not 6+2) and it is 3x12v.



This crap PSU you mean?


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## PLSBX (Jul 3, 2016)

Yea 
It is like "burn-everything".


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## P4-630 (Jul 3, 2016)

PLSBX said:


> Yea
> It is like "burn-everything".



I don't get it, what are you up to.


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## PLSBX (Jul 3, 2016)

Just trying understand why 6pin is rated as 75w.


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## RejZoR (Jul 3, 2016)

PLSBX said:


> Just trying understand why 6pin is rated as 75w.



I'm actually wondering the same. If 8pin has 2 useless pins, what difference does it then make whether it's 6 or 8 pin? Is the sensing pin of any real use regarding 150W power delivery?


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## Beastie (Jul 3, 2016)

8 pin has three grounds as opposed to only two on 6 pin. There's one difference.


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## PLSBX (Jul 3, 2016)

Beastie said:


> 8 pin has three grounds as opposed to only two on 6 pin. There's one difference.


grounds? Not 12v rail? 

Hmm... did anyone test how it can deliver before burn?


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## R-T-B (Jul 3, 2016)

> Hmm... did anyone test how it can deliver before burn?



People have been using these connectors for years at load without burning up, so yeah.


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## Beastie (Jul 3, 2016)

We're going round and round in circles now.


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## PLSBX (Jul 3, 2016)

So.. is 6pin to 8pin safe?


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## R-T-B (Jul 3, 2016)

PLSBX said:


> So.. is 6pin to 8pin safe?



Depends on the gauge of the wire more than anything, but to be completely honest, probably yes.  I still wouldn't risk it though because most 6 pins are wired with thinner gauge wire.



Beastie said:


> We're going round and round in circles now.



Pretty much.  I think the crux of the confusion is that the 6pin connector can actually deliver quite a bit more than it's rated power in it's traditional config.   Not always though, which is why I don't recommend adapters.  Just get a good PSU, any will have an 8pin plug or two if you need them.


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## PLSBX (Jul 3, 2016)

Good PSU should have good cables and pins right?


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## P4-630 (Jul 3, 2016)

PLSBX said:


> Good PSU should have good cables and pins right?



And your PSU probably isn't one of the "good" ones...


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## PLSBX (Jul 3, 2016)

I dont have that shitty modecom.. mine is evga 430w(With pcie 6+2pin).. not best but much better


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## HTC (Jul 3, 2016)

PLSBX said:


> Just trying understand why 6pin is rated as 75w.



I found this video to be quite informative:










This is from a RX480 card BUT it explains this quite nicely.


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## PLSBX (Jul 3, 2016)

I will watch it later.

I think it's end of topic.
How can i mark it as solved?


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## Kissamies (Jul 3, 2016)

My old Corsair HX620 has 6pins on the PSU and 8pins on PCIE cable. Modular cables I mean.

6pin can deliver the same as 8pin.


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## PLSBX (Jul 3, 2016)

So 6pin to 8pin adapter is safe if PSU is good.


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## HTC (Jul 3, 2016)

Please watch the video i posted: it explains why the problem is NOT whatever PSU you have.


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## dorsetknob (Jul 3, 2016)

PLSBX said:


> pcie 6+2pin



PCI 6 Pin+2 = 8pin   ( with the capability of disconnecting the +2 where its not needed)


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## laszlo (Jul 3, 2016)

pci 6 pin provide same power as 8 pin 

the extra 2 pin up to 8 are useless ground from same common ground as the others

the 2nd 12V pin from 6 pin connector is not in use on vga PCB's so only two 12V provide power;these two provide min. 120 W not 75W 

the three 12V pins from 8 pin connector ,all used on vga PCB, provide more than 150 W somewhere in range of min.220 W 

as i see industry standards underrated all and is a big margin which allow the OC

before anyone ask how two 12V rail provide 120W:

molex 12V rail is rated 60W
2 molex to 8 pin adapter has two molex 12 V rail..... so 2*60W=120 W but 8 pin is rated 150W so it can draw 75w from each rail....


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## Jetster (Jul 3, 2016)

I suggest you get a proper PSU. So no 6 pin in a 8 pin. Not even an adapter


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## Solaris17 (Jul 3, 2016)

PLSBX said:


> Good PSU should have good cables and pins right?



good PSU shouldnt require you to use a 6 to 8 pin adapter.


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## PLSBX (Jul 3, 2016)

So i have good PSU? I only asked about differences.


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