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Nvidia's RTX 5090 power connectors are melting

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Re: Nvidia's RTX 5090 power connectors are melting

#281

Post by aaronmdjones »

Kirby64 wrote: post #243
RetpolineDrama wrote: post #231

Earlier quoted context omitted.

I pulled a fresh 20A (120V) circuit just for my 5090 build.

What power supply do you have that even has a 20A inlet? 20 amp breakers are common for outlets (especially in newer builds) but the outlets are still 15A outlets. And there is essentially no desktop power supply that exists that would exceed a 15A outlet currently.

> What power supply do you have that even has a 20A inlet?

ATX PSUs usually have IEC 60320 C14 inlets. The IEC 60320 standard itself states that this inlet is only good for up to 10 Amps.

UL is happy to ignore them and say that 15 Amps is okay. It wouldn't surprise me if someone else were happy to ignore that and say that 20 Amps is okay.

Even still, swapping a C14 inlet for a C20 inlet (IEC max 16 Amps, UL max 20 Amps) would be a relatively easy thing to do (EDIT: on a PSU that is already designed to take more than 15 Amps, obviously). Probably a warranty-voiding action though.

Re: Nvidia's RTX 5090 power connectors are melting

#282

Post by kersplody »

michaelt wrote: post #144
KeplerBoy wrote: post #119

Earlier quoted context omitted.

If only we had connectors which could actually handle such currents. Maybe something along the lines of an XT90, but no Nvidia somehow wants to save a bit of space or weight on their huge brick of a card. I don't get it.

The USB-C connectors on laptops and phones can deliver 240 watts [1] in a 8.4x2.7mm connector. 12VHPWR is 8.4x20.8mm so it's got 7.7x the cross-sectional area but transmits only 2.5x the power. And 12VHPWR also has the substantial advantage that GPUs have fans and airflow aplenty. So I can see why someone looking at the product might have thought the connector could reasonably be shrunk. Of course, the trick USB-C us…

The connector could reasonably be shrunk. It just now has essentially no design margin so any minor issue immediately becomes major! 50A DC is serious current to be treated with respect. 5A DC is sanely manageable.

Re: Nvidia's RTX 5090 power connectors are melting

#283

Post by perching_aix »

gambiting wrote: post #186
cranium wrote: post #80

There is a real problem with the connector design somewhere: der8auer tested with his own RTX 5090FE and saw two of the cable strands reach concerning temperatures (>150ºC). Video timestamp: https://youtu.be/Ndmoi1s0ZaY?t=883

I've tested my own 5090FE the same way he did(Furmark for at least 5 minutes at max load, but I actually ran it for 30 minutes just to be mega sure) and with an infrared thermometer the connector is at 45C on the GPU side and 32C on the PSU side. I have no idea what's happening in his video but something is massively wrong, and I don't understand why he didn't just test it with another PSU/cable.

More peeking and prodding would definitely have been welcome, but it's still a useful demonstration that the issues around the card's power balancing are not theoretical, and can definitely be the culprit behind the reports.

Re: Nvidia's RTX 5090 power connectors are melting

#284

Post by mschuster91 »

KeplerBoy wrote: post #119
DannyBee wrote: post #97

Earlier quoted context omitted.

This is because they are trying to parallel like 50amps (it's 12 volt IIRC) over a few conductors to get to 600watts. If it becomes unbalanced due to any number of reasons, none of those individual cables can come close to handling it - they will all generate enough heat to melt lots of things. Conservatively, they'd have to be 8awg each to be able to handle the full load without melting if they ended up taking the f…

If only we had connectors which could actually handle such currents. Maybe something along the lines of an XT90, but no Nvidia somehow wants to save a bit of space or weight on their huge brick of a card. I don't get it.

> If only we had connectors which could actually handle such currents.

The problem isn't connectors, the problem (fundamentally) is to share electric connectivity between multiple conductors.

Sure, you can run 16A over 1.5 mm² wires, and 32A over 2.5 mm² (taken from [1], yes it's for 230V but that doesn't matter, the current is important not the voltage). And theoretically you could run 32A over 2x 1.5 mm² (you'd end up with 3 mm² cross section), but it's not allowed by code as when, for any reason, either of the two legs disconnects entirely or has increased resistance e.g. due to corrosion or a loose screw / wire nut (hence, please always use Wago style clamps - screws and wire nuts are not safe, even if torqued properly which most people don't), suddenly the other leg has to carry (much) more current than it's designed for and you risk anything from molten connectors to an outright fire. And that is what NVidia currently is running into, together with bad connections (e.g. due to dirt ingress).

The correct solution would be for the GPU to not tie together the incoming individual 12VHPWR pins on a single plane right at the connector input but to use MOSFETs and current/voltage sense to detect stuff like different current availability (at least it used to be the case with older GPUs that there were multiple ways to supply them with power and only, say, one of two connectors on the GPU being used) or overcurrents due to something going bad. But that adds complexity and, at least for the overcurrent protection, yet another microcontroller plus one ADC for each incoming power pin.

Alternatively each 12VHPWR pair could get its own (!) DC-DC converter down to 1V2 or whatever the GPU chip actually needs, but again that also needs a bunch of associated circuitry.

Another and even more annoying issue by the way is grounding - because all the electricity that comes in also wants to go back to the PSU and it can take any number of paths - the PCIe connector, the metal backplate, the 12VHPWR extra connector, via the shield of a DP cable that goes to a Thunderbolt adapter card's video input to that card, via the SLI connector to the other GPU and its ground...

Electricity is fun!

[1] https://stex24.com/de/ratgeber/strombelastbarkeit

Re: Nvidia's RTX 5090 power connectors are melting

#285

Post by tcdent »

kersplody wrote: post #273

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…

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.

Re: Nvidia's RTX 5090 power connectors are melting

#286

Post by roland35 »

Havoc wrote: post #77

What’s wild is that this is a company clearly capable of designing highly complex things with numerous tradeoffs, challenges and unknowns. And then the fuckin cable is the issue. Repeatedly.

Cables are hard! Back when I did EE work we tried to avoid cables as much as possible because they cause all sorts of annoyances

Re: Nvidia's RTX 5090 power connectors are melting

#287

Post by ryao »

cesarb wrote: post #214
baq wrote: post #171

Earlier quoted context omitted.

At these wattages just give it its own mains plug.

> At these wattages just give it its own mains plug. You might think you're joking, but there are gamer cases with space for two PSUs, and motherboards which can control a secondary PSU (turning both PSUs on and off together). When using a computer built like that, you have two main plugs, and the second PSU (thus the second mains plug) is usually dedicated to the graphics card(s).

Server systems already work like this for redundancy.

Re: Nvidia's RTX 5090 power connectors are melting

#288

Post by jgalt212 »

jorgemf wrote: post #251
rollcat wrote: post #242

Earlier quoted context omitted.

Can we talk about how absolutely terrifying is that 600W figure? We're not transcoding or generating slop as the primary use case, we're playing computer games . What was wrong with the previous-generation graphics that we still need to push for more raw performance, rather than reducing power draw?

This genereation seems that is getting performance using more power and more cores. Not really an architectural change but only packing more things in the chip that require more power.

Too true. I've been looking replace my 1080. This was a beast in 2016, but the only way I can get a more performant card these days is to double the power draw. That's not really progress.

Re: Nvidia's RTX 5090 power connectors are melting

#289

Post by beeflet »

onli wrote: post #5
lyu07282 wrote: post #4

It's strange how Nvidia just doubled down on a flawed design for no apparent reason. It doesn't even do anything, the adapter is so short you still have the same mess of cables in the front of the case as before.

I was under the impression it saves them money. Is that correct? It is also a powerplay. By potentially introducing a PSU connector AMD and Intel do not use they abuse their market power to limit interoperability. Plus probably some internal arrogance about not admitting failures.

>By potentially introducing a PSU connector AMD and Intel do not use they abuse their market power to limit interoperability.

I suppose but this could be overcome by AMD/Intel shipping an adapter cable

Re: Nvidia's RTX 5090 power connectors are melting

#290

Post by zamalek »

kersplody wrote: post #273

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…

> 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.

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