[kersplody]

12vhpwr has almost no safety margin. Any minor problem with it rapidly becomes major. 600W is scary, with reports of 800W spikes.

12V2x6 is particularly problematic because any imbalance, such as a bad connection of a single pin, will quickly push things over spec. For example, at 600W, 8.3A are carried on each pin in the connector. Molex Micro-Fit 3.0 connectors are typically rated to 8.5A -- That's almost no margin. If a single connection is bad, current per connector goes to 10A and we are over spec. And this if things are mated correctly. 8.5A-10A over a partially mated pin will rapidly heat up to the point of melting solder. Hell, the 16 gauge wire typically used is pushing it for 12V/8.5A/100W -- that's rated to 10A. Really would like to see more safety margin with 14 gauge wire.

In short, 12V2x6 has very little safety margin. Treat it with respect if you care for your hardware.

[ckozlowski]

Great summary. Buildzoid over on YouTube came to a similar conclusion back during the 4xxx series issues[1], and looks like he's released a similar video today[2]. It's worth a watch as he gets well into the electrical side of things.

It's been interesting to think that we're probably been dealing with poor connections on the older Molex connectors for years, but because of the ample margins, it was never an issue. Now with the high power spec, the underlying issues with the connectors in general are a problem. While use of sense pins sorta helps, I think the overall mechanism used to make an electrical connection - which hasn't changed much in 30+ years - is probably due for a complete rethink. That will make connectors more expensive no doubt, but much of the ATX spec and surrounding ecosystem was never designed for "expansion" cards pushing 600-800w.

[1] - 12VHPWR failures (2023) https://youtu.be/yvSetyi9vj8?t=1479 [2] - Current issues: https://www.youtube.com/watch?v=kb5YzMoVQyw

[exmadscientist]

> I think the overall mechanism used to make an electrical connection - which hasn't changed much in 30+ years - is probably due for a complete rethink.

There are tons of high-power connectors out there, and they look and work pretty much the same as the current ones (to the untrained eye). They are just more expensive.

Though at 40A+ you tend to see more "banana" type connectors, with a cylindrical piece that has slits cut in it to deform. Those can handle tons of current.

[opello]

This [1] is also a good deep dive into the space covering the spec, limits, and materials details. For example:

> The specification for the connector and its terminals to support 450 to 600W is very precise. You are only within spec if you use glass fiber filled thermoplastic rated for 70°C temperatures and meets UL94V-0 flammability requirements. The terminals used can only be brass, never phosphor bronze, and the wire gauge must be 16g (except for the side band wires, of course).

[1] http://jongerow.com/12VHPWR/

[amluto]

And yet plenty of things around the house use far more than 800W and work fine. The secret is to use a more reasonable voltage.

30V or 36V or even 48V would leave a decent margin for touch safety and have dramatically lower current and even more dramatically lower resistive loss.

[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.

[zamalek]

> Any imbalance

I watched de-Bauer's analysis this morning, and you've seemingly hit the nail on the head. Even on his test bench it looks like only two of the wires are carrying all of the power (instead of all of them, I think 4 would be nominal?) - using a thermal camera as a measuring tool. The melted specimen also has a melted wire.

Maybe 24V or 48V should be considered, and higher gauge wires - yes.

[mjevans]

It would be _lovely_ if instead of the 12V only spec we went to 48V for internal distribution. Though that would require an ecosystem shift. USB-PD 2.0~3.0 would also be better supported https://en.wikipedia.org/wiki/USB_hardware#USB_Power_Deliver...

As others no doubt mention Power (loss, Watts) = I (amsp) * V (volts (delta~change on the wire)).

dV = I*R ==> dV = I * I / R -- That is, other things being equal, amps squared is the dominant factor in how much power loss occurs over a cable. In the low voltage realms most insulators are effectively the same and there's very little change in resistance relative to the voltages involved, so it's close enough to ignore.

600W @ 12V? 50A ==> 1200 * R while at 48V ~12.5A ==> 156.25 * R

A 48V system would have only ~13% the resistive losses over the cables (more importantly, at the connections!); though offhand I've heard DC to DC converters are more efficient in the range of a 1/10th step-down. I'm unsure if ~1/25th would incur more losses there, nor how well common PC PCB processes handle 48V layers.

https://en.wikipedia.org/wiki/Low_voltage#United_States

""" In electrical power distribution, the US National Electrical Code (NEC), NFPA 70, article 725 (2005), defines low distribution system voltage (LDSV) as up to 49 V.

The NFPA standard 79 article 6.4.1.1[4] defines distribution protected extra-low voltage (PELV) as nominal voltage of 30 Vrms or 60 V DC ripple-free for dry locations, and 6 Vrms or 15 V DC in all other cases.

Standard NFPA 70E, Article 130, 2021 Edition,[5] omits energized electrical conductors and circuit parts operating at less than 50 V from its safety requirements of work involving electrical hazards when an electrically safe work condition cannot be established.

UL standard 508A, article 43 (table 43.1) defines 0 to 20 V peak / 5 A or 20.1 to 42.4 V peak / 100 VA as low-voltage limited energy (LVLE) circuits. """

The UK is similar, and the English Wikipedia article doesn't cite any other country's codes, though the International standard generally talks at the power grid distribution level.

[magicalhippo]

From what I can gather, one challenge with 24V and higher is that switched-mode converters, such as the buck converters used in the power stage, get a lot more inefficient when operating at high ratios.

You can see this effect in figure 6 in this[1] application note, where it's >90% efficient at ratios down to 10:2.5, but then drops to ~78% at a ratio of 10:1.

So if one goes for higher voltage perhaps 48V would be ideal, and then just accept the GPU needs a two-stage power conversion, one from 48V to 12V and the other as today.

The upside is that this would more easily allow for different ratios than today, for example 48V to 8V, then 8V to 1.2V, so that each stage has roughly the same ratio.

[1]: https://fscdn.rohm.com/en/products/databook/applinote/ic/pow... (page 14)

[crote]

> I think 4 would be nominal?

6 or 12, depending on how you count. There are 6 12V supply wires, and 6 GND return wires. All of them should be carrying roughly the same current - just with the GND wires in the opposite direction from the 12V ones.

[snuxoll]

> Really would like to see more safety margin with 14 gauge wire.

The wire itself really isn't the issue, the NEC in the US is notoriously cautious and 15A continuous is allowed on 14AWG conductors. Poor connectors that do not ensure good physical contact is a real problem here, and I really fail to understand the horrid design of the 12VHPWR connector. We went decades with traditional PCIe 2x6 and 2x6 power connectors with relatively few issues, and 12VHPWR does what over them? Save a little bulk?

[exmadscientist]

This can't be Micro-Fit 3.0, those are only sized to accept up to 18AWG. At least, with hand crimp tooling, and that's dicey enough that I'd be amazed if Molex allowed anything larger any other way. The hand crimper for 18AWG is separate from the other tools in the series, very expensive, and a little bit quirky. Even 18AWG is pushing it with these terminals.

This has to be some other series.

[Xelbair]

There were some tests of current draw being imbalanced on each pair.

two cables carried 22A - PSU connector heating up near them to 150C

rest 2-3A. derbauer has video on that on youtube.

1st party cables too.

connector is also a disaster design wise.

[choilive]

I would bet a lot of money more than 1 engineer at nvda flagged this as a potential issue. If you were going to run this close to the safety margin, I would at minimum add current sensing on each pin.

[amelius]

Yes, and by the way I also think typical GPU cables are way too stiff for such a small and fragile connector.

[opello]

Shouldn't there be a bit better margin if we subtract the 75W from the slot itself? Down to ~7.3A/pin in the 600W example.

[HexPhantom]

At what point do we stop blaming user error and start admitting the design itself is the problem?

[caycep]

RTX 6000 Ada Gen had EPS12V 8 pin or something?

[Dalewyn]

What is the reason the spec keeps specifying next to no headroom? Clearly that was the fundamental problem with 12VHPWR and it's being repeated with 12V2X6.

Any engineer worth his salt knows that you should leave plenty of headroom in your designs, you are not supposed to stress your components to (almost) their maximum specifications under nominal use.

[bcrl]

I found it hilarious when a friend went to use a Tesla supercharger on his F150 Lightning. As the cable is only long enough to reach the charge port on the corner of a Telsa, he had to block 2 parking spaces and almost 3 chargers to use it. Oops... I hope all the money "saved" on copper was worth it.