I turned a dual molex to CPU 8 pin adapter into a PCIe adapter, but..

[thekingofmonks]

I did that simply by rewiring the pins and cutting the edges of two square shaped feet, however I’m skeptical of its use as an 8 pin PCIe connector.

 

For a long time I’ve been using a molex to 6 pin adapter which ran fine, but I don’t know whether the two last pins of this 8 pin mod are required to be contacted or not.

 

According to this pinout scheme, one is for ground/return and the other is for sense, which I feel like are essential for a card to work, am I right? If so, what would I have to wire them to on the molex end of the adapter?

 

 

Thanks in advance!

[whispous]

NO NO NO NO NO

 

DO NOT DO THIS

 

None of this is safe for your components or yourself. It is not designed to work like this.

 

Why are you doing this? Just get a proper PSU with the cables you need.

[IkeaGnome]

Molex is rated for 54 watts. Your 8 pin PCIE is rated for 150. It's not the same even if you got the sense and ground wires working. You're asking to melt wires.

[Helpful Tech Witch]

GOD NO
MOLEX TO PCIE IS KNOWN TO  FAIL  ALL THE TIME

Unless you want to kill the gpu, dont use a molex to pcie adaptor

[thekingofmonks]

1 hour ago, IkeaGnome said:

Molex is rated for 54 watts. Your 8 pin PCIE is rated for 150. It's not the same even if you got the sense and ground wires working. You're asking to melt wires.

No. Two molex cables will make a combined wattage of 110W (2x 5V x 11A with the absence of 12V). My PSU’s 5V rail can supply a maximum of 130W, so I’m absolutely good here to supply a single video card alongside two storage devices. The card would be under powered (if rated at higher than 110W), so let alone the fact that the wires would melt or anything of the kind. Depending on its requirements, it’ll either work or fail, but definitely won’t die or cause a fire… The adapter should function just like a 6 pin adapter as long as I wire both pins correctly. Only problem is that I won’t ever get the card to run as fast as intended.

 

One of the ground wires on the molex end is routed to the main sense pin, so the second sense pin on an 8 pin connector should at least be touted to another ground, either from the molex end or just shorted on the PCIe end. Seems like I’ve found the solution to my own problem.

[thekingofmonks]

1 hour ago, HelpfulTechWizard said:

GOD NO
MOLEX TO PCIE IS KNOWN TO  FAIL  ALL THE TIME

Unless you want to kill the gpu, dont use a molex to pcie adaptor

Fortunately, it has not failed me a single time, at least with a 650Ti. Underpowered hardware does not always end up failing, and surely won’t die.

[thekingofmonks]

1 hour ago, whispous said:

NO NO NO NO NO

 

DO NOT DO THIS

 

None of this is safe for your components or yourself. It is not designed to work like this.

 

Why are you doing this? Just get a proper PSU with the cables you need.

Not designed to work this way, but electrically it should and does work. I’m tired of all the skepticism about this, tons of people used to have adapters on their mid-range cards back in the kepler/GCN days. I need answers, not fear in my replies, ffs…

[thekingofmonks]

1 minute ago, Caroline said:

ground to ground and leave sense empty, it's not required for the card to power up

 

About the wattage, it *could* work but it's certainly not the best way to add a connector to a power supply, if you know internals go ahead and solder the wires (except for sense) directly to the board to avoid using these monstrosities called adapters.

Thank you very much, that was a much more appreciable reply than the others.

[heatonpkmassive]

Whether or not this is a good idea depends on 3 things:

The brand and model of your power supply.

The gauge of the wires in your adapters.

The card you are running.

[heatonpkmassive]

Might wanna check this thread:
 

 

[Ralf]

3 hours ago, thekingofmonks said:

No. Two molex cables will make a combined wattage of 110W (2x 5V x 11A with the absence of 12V). My PSU’s 5V rail can supply a maximum of 130W, so I’m absolutely good here to supply a single video card alongside two storage devices. The card would be under powered (if rated at higher than 110W),

I would like to know why you list the 5V wattage. Are you trying to power the gpu with 5V?

 

There is no such thing as under powered card, it will draw as much power as it needs.

[thekingofmonks]

10 hours ago, Ralf said:

I would like to know why you list the 5V wattage. Are you trying to power the gpu with 5V?

 

There is no such thing as under powered card, it will draw as much power as it needs.

Molex adapters do not use 12V. Only three pins are present if you look at the picture of any molex to PCIe adapter. I assume the reason why they don't use 12V is because the 12V rail is needed for the main ATX connectors (especially CPU), and if that were used on a video card, it might cause instability to the system.

 

As to cards drawing as much power as they need on a limited rail, that is simply not possible. Voltage is fixed, and despite amperage being modulable, it still has a limit of its own on the rail, and other devices running on the same rail will restrict the card's draw.

[Ralf]

2 hours ago, thekingofmonks said:

Molex adapters do not use 12V. Only three pins are present if you look at the picture of any molex to PCIe adapter. I assume the reason why they don't use 12V is because the 12V rail is needed for the main ATX connectors (especially CPU), and if that were used on a video card, it might cause instability to the system.

 

As to cards drawing as much power as they need on a limited rail, that is simply not possible. Voltage is fixed, and despite amperage being modulable, it still has a limit of its own on the rail, and other devices running on the same rail will restrict the card's draw.

So the picture in the OP where it says the PCIe connector has 12V is wrong? Or do the PSU's PCIe connector have 12V, but the molex adapter is 5V and the gpu has a step up converter built in?

Why do the pre 2018 Seasonic Focus shut down on high power draw gpu's like Vega or 3090?

The over-power protection (OPP) that kicks in when the power we pull from a PSU exceeds its maximum rated capacity is useless since the devices you run wont ever trigger it, correct?

[thekingofmonks]

11 minutes ago, Ralf said:

So the picture in the OP where it says the PCIe connector has 12V is wrong? Or do the PSU's PCIe connector have 12V, but the molex adapter is 5V and the gpu has a step up converter built in?

Why do the pre 2018 Seasonic Focus shut down on high power draw gpu's like Vega or 3090?

The over-power protection (OPP) that kicks in when the power we pull from a PSU exceeds its maximum rated capacity is useless since the devices you run wont ever trigger it, correct?

That picture only shows the pinouts of PCIe 6 and 8 pin and ATX CPU 4 and 8 pin connectors. Molex connectors have four pins: 5V, gnd, gnd and 12V. The adapter has two molex connectors but lacks wiring for the 12V pins. It routes the 5V pins to each of the 12V IN pins of the PCIe end, either directly (for 6 pins) or by splitting (8 pins). This always end up with the graphics card being underpowered, no matter what.

 

There won't ever be OPP because there simply isn't enough power to feed the card the way it was designed to, let alone overpowering it. No dangers, no OPP.

 

The only reasons why a molex adapter would melt or burn is either because it has pins in contact when they're not supposed to, or if there's too much stress (overcurrent) in the wires, which is caused by poor control of the rails (in this case 5V) within the PSU.

[Ralf]

18 minutes ago, thekingofmonks said:

That picture only shows the pinouts of PCIe 6 and 8 pin and ATX CPU 4 and 8 pin connectors. Molex connectors have four pins: 5V, gnd, gnd and 12V. The adapter has two molex connectors but lacks wiring for the 12V pins. It routes the 5V pins to each of the 12V IN pins of the PCIe end, either directly (for 6 pins) or by splitting (8 pins). This always end up with the graphics card being underpowered, no matter what.

 

There won't ever be OPP because there simply isn't enough power to feed the card the way it was designed to, let alone overpowering it. No dangers, no OPP.

 

The only reasons why a molex adapter would melt or burn is either because it has pins in contact when they're not supposed to, or if there's too much stress (overcurrent) in the wires, which is caused by poor control of the rails (in this case 5V) within the PSU.

Not sure if trolling or serious.

@jonnyGURU

[thekingofmonks]

12 minutes ago, Ralf said:

Not sure if trolling or serious.

@jonnyGURU

I never said I was absolutely firm with everything I've said, but no one has tried to explain otherwise for the past 17 hours. I can't know whether I'm 100% right or not. I'm only basing myself on the most that I know.

[heatonpkmassive]

17 hours ago, heatonpkmassive said:

Whether or not this is a good idea depends on 3 things:

The brand and model of your power supply.

The gauge of the wires in your adapters.

The card you are running.

So what are your answers to these questions? That will largely determine whether what you are saying has any credence.

[thekingofmonks]

8 minutes ago, heatonpkmassive said:

So what are your answers to these questions? That will largely determine whether what you are saying has any credence.

I do not see a question, I thought you were making a statement?

[heatonpkmassive]

10 minutes ago, thekingofmonks said:

I do not see a question, I thought you were making a statement?

Okay, I'll formulate it as you want it.

 

What is the brand and model of your power supply?

What is the gauge of the wires in your adapters?

What is the card you are running using these adapters?

Now they are questions, I'm actually trying to help you make your point..

[Guest]

8 hours ago, Ralf said:

Not sure if trolling or serious.

@jonnyGURU