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?

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.

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?

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

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:

PLSBX · Jul 2, 2016

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

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.

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.

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?

PLSBX · Jul 3, 2016

Almost.. one more question.

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

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?

PLSBX · Jul 3, 2016

Yea

It is like "burn-everything".

P4-630 · Jul 3, 2016

PLSBX said:
Yea
It is like "burn-everything".

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

PLSBX · Jul 3, 2016

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

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?

Beastie · Jul 3, 2016

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

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?

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.

Beastie · Jul 3, 2016

We're going round and round in circles now.

PLSBX · Jul 3, 2016

So.. is 6pin to 8pin safe?

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.

PLSBX · Jul 3, 2016

Good PSU should have good cables and pins right?

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...

PLSBX · Jul 3, 2016

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

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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PCIe 6pin, 8pin - differences

PLSBX

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R-T-B

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Jetster

newtekie1

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PLSBX

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PLSBX

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P4-630

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RejZoR

Beastie

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