[tcdent]

This is the most informative assessment in this thread.

You'd expect to see the capacity to be 125% as is common in other electrical systems.

Ratings for connectors and conductors comes with a temperature spec as well, indicating the intended operating temperature at a load. I'm sure, with this spec being near the limit of the components already, that the operating temperatures near full load are not far from the limit, either.

Couple that with materials that may not have even met that spec from the manufacturer and this is what you get. Cheaper ABS plastic on the molex instead of Nylon, PVC insulation on the wire instead of silicone, and you just know the amount of metal in the pins is the bare minimum, too.

[zamalek]

"3rD party connectors" is being waved around by armchair critics. The connectors on the receiving end of all of this aren't some cheap knock-off, they are from a reputable manufacturer and probably exceed the baseline.

[Ygg2]

No sane individual is going to buy 5090 for $2000-100000 and hook it up to a $15 Power supply.

[rincebrain]

Correct, but it turns out, a fair fraction of the people who day 1 purchase a GPU for that much may not necessarily be described as wholly sane.

[m463]

your comment makes me wonder...

Is it a computer science type person, who might be unaware of electrical engineering...

Or someone who takes a perfectly good car and adds ridiculous rims that rub?

[Ygg2]

They aren't insane, just not thrifty with their money.

[lmm]

Doesn't mean they prioritise everything the same way. Plenty of people buy an expensive car and put cheap tires on it or what have you.

[asddubs]

Yeah, I can easily see someone buying an expensive GPU but a cheap power supply because they ostensibly all do the same thing

[rincebrain]

They're not necessarily insane, I agree.

But I've also known some people who did that when they did not have the disposable income to do it.

[Decabytes]

Let's not forget that the 90 series cards in each generation won't be top end forever. Soon they will just be used cards like all other technology. And someone might be building their first computer, got a good deal on eBay on a 5090 which is 5 or 6 generations old, and cobble it together with some other old parts, and maybe a weak PSU, or an older 12vHP cable

[clhodapp]

The cable must necessarily be third-party from the perspective of the GPU or from the perspective of the power supply.

If it's built to the expected tolerance, it should work.

[Dalewyn]

Except when the "expected tolerance" is unreasonable.

Even if the connectors and wires are to spec, the design leaves next to no margin for play. You need that margin to account for reality: Handling by casual end-users rather than trained professionals, the ambient temperature of the average room or office, dirt and grime that might get lodged and go unnoticed, wonky supply/draw of power, and more.

Running 8.3A through connections rated for 8.5A is "expected tolerance", it's also fucking stupid in no uncertain terms.

[clhodapp]

There are at least two issues here:

1) The designed safety margin is unacceptably low. It should be set such that any cable that complies with the expected safety tolerance for carrying current is safe to use.

2) The late-model Nvidia cards in particular have no feedback system to discover unbalanced current on 12v wires that make up the connector and no circuitry to keep the current balanced even if they did. That is, they forgo any digital control and depend on the physical properties of the conductors to be perfectly balanced.

Overall, Nvidia failed to learn from the melting connector issues in the RTX 4000 series and doubled down by increasing the power draw while further cost-cutting the safety circuitry.

See:

    * High-level demonstration: https://youtu.be/Ndmoi1s0ZaY?si=bkv12pXG4K5T72YN
  
    * Low-level explanation: https://youtu.be/kb5YzMoVQyw?si=Bl5aowND4uXoI8s6

[caycep]

Ok, I have to say this, but the narrator sounds a lot like Jim Henson/Kermit the Frog....(my understanding it is a maryland/mississippi accent combo)

[sozforex]

~23A had been measured going going through one of 6 wires/pins in this test: https://youtu.be/Ndmoi1s0ZaY?t=927

Standard requires these connectors to handle 9.5A per pin (9.5 A × 12 V × 6 pin = 684 W).

A detailed explanation of this mess: https://www.youtube.com/watch?v=kb5YzMoVQyw

[leeter]

I'm curious, if there are any high level electrical engineers reading this please respond.

I wonder if that vertical (as far as the PCB goes) power connector will always ensure that this sort of imbalance will always occur. While we like to pretend that current is even in any given current plane that's not what happens. The impedance of the wires and copper is not perfectly ideal. This is why these connectors have equal number of grounds, so they have an ideal shortest path and balanced return current path. So I'm curious if electrically it's just impossible to have a vertical connector like that (on that shorts all the pins for 12V together instead of current balancing them) and have it balance current across the pins. The pins closest to the board should in theory have the greatest currents as they are the shortest path electrically. Based on the pictures that appears to be the case. It appears that the pins under the most stress are likely those with the lowest impedance.

Assuming my SWAG above is correct... I'm curious if this is affected by the per pin impedance on the PSU too. Where if certain folks are just unlucky get a situation where some pins in the connector have a significantly lower impedance than the rest.

If my second SWAG is plausible, my third and really bad SWAG is that removing the two ground pins nearest the PCB could actually "balance" the current better by forcing the current to use a slightly longer path for the power pins. But, my guess is this will just cause EMI issues. So please don't test this unless you're an EE and know what you're doing.

This is pure speculation on top of what Buildzoid, the posts above this have said, and what I've learned from Robert Feranec's videos. I'm in no way an electrical engineer, just a humble hobbyist and person that loves to learn.

[exmadscientist]

Paralleling wires is stable because the TCR of copper is positive. When one connection carries too much current compared to its peers, it will heat up. This will increase its resistance, causing it to accordingly carry less of the current. So the system is self-balancing.

Do not remove ground wires. That is stupid. You'll just be raising the current in the remaining wires. EMI should not be a major concern as we are talking about DC power delivery here (also why I'm saying "resistance" instead of "impedance") and so the potential for trouble by changing the number of conductors making a connection is limited. Yes, anything could happen, but that's just the nature of EMC problems.

[toast0]

> This is why these connectors have equal number of grounds, so they have an ideal shortest path and balanced return current path.

These connectors have an equal number of grounds and 12v because the same current flows on both sides, and the required current justifies at least 6 wires at the specified current.

Pci-e 8-pin power is a bit weird, because it's 3 12v and essentially 5 grounds; but that's because it's pci-e 6 pin and a promise that the power supply makers know what they're doing... The extra 2 grounds signal that the PSU designers are aware of the higher current limit, even though the wiring specifications are the same.

[tcdent]

Show me the Molex logo molded on that connector end and I'll believe you.

It's all off-brand slop from companies that learned marketing by emulating western brands. Kids on the internet lap up circuitous threads about one brand being better than the other based on volume.

"MODDIY" is a reputable brand? C'mon.