Question 12VHPWR Sense Pins

[SyCoREAPER]

Not sure if here or GPU is more appropriate. Moderators at your discretion.


Quick question everyone. Maybe I'm looking at this entirely wrong. I bought a 4x8 to 12VHPWR adapter. Sense 0 is looped into Sense 1. If the below diagram says that both need to be grounded for 600w doesn't that mean my cable is OPEN on both pins? If so, can I just cut them for the full 600w?

https://preview.redd.it/9oxot15wnuna1.png

(PS, my card is 600w capable)

Specs to my build;
CPU: i7-13700K (Overclocked)
Cooler: Corsair H150 Elite Caprellix 360mm
RAM: DDR4 G-Skill 4000Mhz (4x16GB, Gear1)
MB: MSI Edge z690 DDR4 WiFi
GPU: MSI Gaming Trio 4090 (Custom SuprimX vBIOS)
PSU: MSI MPG A1000G PCIE5

 

[Lutfij]

Your URL doesn't work for me. Might want to host your image on a site akin to Imgur and then pass on the URL for us to see.

Shoehorned your specs since sig space specs can and will change over time, rendering this thread and any probable solutions moot to the person in the same boat as you're in now.

I bought a 4x8 to 12VHPWR adapter.
What happened to the one that came with the GPU?

 

[SyCoREAPER]

So more in depth, I'm building a friend a PC.

The 4090 I have (MSI Trio) can easily do 600w, been doing it for months. This card was able to accept custom BIOS' with the old TechSpot tool way before the recent one came out.

The card comes with a 3 x 8, that isn't sufficient from my research for 600w, only 450w.

The PSU does not have 12VHPWR (by my design). With the 5090s, it's rumored and probable that 12VHPWR will be phased out. Most PSUs with a 12VHPWR have fewer PCIe power ports (usually 5 but need 6).

So I bought this 4 x 8 adapter but sense pins 0 and 1 are looped into each other. Id expect that to be open and not grounded. Grounded is what's needed from my understanding for the card to draw 600w. Looking at a few other similar cables, they are looped too.

Here is the image above that you weren't able to open. (Source)

 

[hotaru.hino]

They're connected together with one of them being connected to ground. This is a common thing in cabling if you need to tie multiple signal lines to ground.

They do this with PCIe PEG sense pins too.

 

[SyCoREAPER]

They're connected together with one of them being connected to ground. This is a common thing in cabling if you need to tie multiple signal lines to ground.

They do this with PCIe PEG sense pins too.

Need clarification on that. If 0 is looped into 1 and there are no other sense wires, whats grounding it?

 

[hotaru.hino]

Need clarification on that. If 0 is looped into 1 and there are no other sense wires, whats grounding it?

Can you take a picture of the 12VHPwr connector side and share it here?

 

[SyCoREAPER]

Went to take a picture and I'm a derp derp.

Sense 0 and 1 are looped into ground. On the connecter. Initially it looked like they were looped to each other.


However this raises a new concern. Specifically the very last paragraph.

Myth Busted: This is how NVIDIA’s 4-way adapter for the 12VHPWR port of the GeForce RTX 4090 really works! | igor´sLAB

Who doesn’t know it, the funny adapter from NVIDIA, with which you can merge four PCIe 6+2 pin cables to be able to run graphics cards with up to 600 watts? If you only connect three plugs…

www.igorslab.de

 

[hotaru.hino]

Went to take a picture and I'm a derp derp.

Sense 0 and 1 are looped into ground. On the connecter. Initially it looked like they were looped to each other.


However this raises a new concern. Specifically the very last paragraph.

Myth Busted: This is how NVIDIA’s 4-way adapter for the 12VHPWR port of the GeForce RTX 4090 really works! | igor´sLAB

Who doesn’t know it, the funny adapter from NVIDIA, with which you can merge four PCIe 6+2 pin cables to be able to run graphics cards with up to 600 watts? If you only connect three plugs…

www.igorslab.de

I think what they're getting at is the official cable has safety features built in in case you for some reason don't plug everything that's needed. Having 600W go through three cables meant to carry 150W each (so 450W total) doesn't sound like a good idea. So the IC chip in Igor's cable is meant to signal to the video card that something's up (assuming the video card even does anything with it). The cables that simple ground the sense wires make it so the 600W is always the upper limit.

However, if it helps you sleep better at night, you should be using either the adapter the card came with or something from your power supply's manufacturer if they have one.

 

[SyCoREAPER]

I think what they're getting at is the official cable has safety features built in in case you for some reason don't plug everything that's needed. Having 600W go through three cables meant to carry 150W each (so 450W total) doesn't sound like a good idea. So the IC chip in Igor's cable is meant to signal to the video card that something's up (assuming the video card even does anything with it). The cables that simple ground the sense wires make it so the 600W is always the upper limit.

However, if it helps you sleep better at night, you should be using either the adapter the card came with or something from your power supply's manufacturer if they have one.

There is problem 3 and I believe the final one unless you mention something next I didn't think of.

Igor is trustworthy and has no stake in the adapter in terms of making money.
He says in that same article that a 3x8 adapter is not enough (that's what I have that came with the card) for 600w, only 450w.

However the first comment on his post made the (math checks out) calculations for the wires and said it does work.
Also, moddiy who sells 3x8 and 4x8, says a 3x8 can easily do 600w. So if they are selling both and the 4x8 costs more but are saying the 3x8 is sufficient.

There's a lot of contradicting information that ive come across.

 

[hotaru.hino]

There is problem 3 and I believe the final one unless you mention something next I didn't think of.

Igor is trustworthy and has no stake in the adapter in terms of making money.
He says in that same article that a 3x8 adapter is not enough (that's what I have that came with the card) for 600w, only 450w.

However the first comment on his post made the (math checks out) calculations for the wires and said it does work.
Also, moddiy who sells 3x8 and 4x8, says a 3x8 can easily do 600w. So if they are selling both and the 4x8 costs more but are saying the 3x8 is sufficient.

There's a lot of contradicting information that ive come across.

Here's the thing. The PCIe spec says that 8-pin PEG connectors must be rated for 150W. That doesn't mean it's rated only up to 150W and in fact, you should never build anything electrical rated just to the thing you said it's rated for unless you're trying to scam people and burn their houses down.

So yes, 8-pin PEG connectors can support more than 150W. And higher quality cables may use cabling that can safely support up to 10A apiece, meaning 120W per line, or 360W per connector. However, it's not wise to assume any cable can do this and at the very minimum the cable manufacturer did their due diligence to meet the spec of 150W.

So who's right? No one. It depends on the cable you get. And unless you have the equipment to verify its electrical specifications, you can only assume that any given 8-pin PEG cable can support up to 150W.

 

[SyCoREAPER]

Here's the thing. The PCIe spec says that 8-pin PEG connectors must be rated for 150W. That doesn't mean it's rated only up to 150W and in fact, you should never build anything electrical rated just to the thing you said it's rated for unless you're trying to scam people and burn their houses down.

So yes, 8-pin PEG connectors can support more than 150W. And higher quality cables may use cabling that can safely support up to 10A apiece, meaning 120W per line, or 360W per connector. However, it's not wise to assume any cable can do this and at the very minimum the cable manufacturer did their due diligence to meet the spec of 150W.

So who's right? No one. It depends on the cable you get. And unless you have the equipment to verify its electrical specifications, you can only assume that any given 8-pin PEG cable can support up to 150W.

Makes sense. Guess I'll try and find an OEM one and otherwise just settle on the grounded loop design rather than risk a 3x8.