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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

#291

Post by ckozlowski »

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…

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

Re: Nvidia's RTX 5090 power connectors are melting

#292

Post by Dylan16807 »

immibis wrote: post #272
Dylan16807 wrote: post #240

Earlier quoted context omitted.

It's not great. Dropping 5V makes power routing more complicated and needs big conversion blocks outside the PSU. I would say it makes sense if you want to cut the PSU entirely, for racks of servers fed DC, but in that case it looks like 48V wins.

There are already huge conversion blocks outside the PSU. That's why they figured there's no need to keep an extra one inside the PSU and run more wiring everywhere. Your CPU steps down 12 volts to 1 volt and a bit. So does your GPU. If you see the big bank of coils next to your CPU on your motherboard, maybe with a heatsink on top, probably on the opposite side from your RAM, that's the section where the voltage get…

Those are actually at the point of use and unavoidable. I mean extra ones that convert to 5V and then send the power back out elsewhere. All those drives and USB ports still need 5V and the best place to make it is the PSU.

Re: Nvidia's RTX 5090 power connectors are melting

#293

Post by michaelt »

6SixTy wrote: post #262
michaelt wrote: post #144

Earlier quoted context omitted.

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…

Nobody thought that they could push 50A at 12V through half the connector. It's management wanting to push industrial design as opposed to safety. They made a new connector borrowing from an already existing design, pushed up the on paper amperage by 3A, never changed the contact resistance, and made the parent connector push current near it's limit (10.5A max vs 8.3A). And oh, the insertion force is so, so much high…

> Nobody thought that they could push 50A at 12V through half the connector.

If you're saying that the connector doesn't have a 2x safety factor then I'd agree, sure.

But I can see how the connector passed through the design reviews, for the 40x0 era cards. The cables are thick enough. The pins seem adequate, especially assuming any GPU that's drawing maximum power will have its fans producing lots of airflow; plenty of connectors get a little warm. There's no risk of partial insertion, because the connector is keyed, and there's a plastic latch that engages with a click, and there's four extra sense pins. I can see how that would have seemed like a belt-and-braces approach.

Obviously after the first round of melted connectors they should have fixed things properly.

I'm just saying to me this seems like regular negligence, rather than gross negligence.

Re: Nvidia's RTX 5090 power connectors are melting

#294

Post by martinpw »

tcdent wrote: post #206
revnode wrote: post #83

Earlier quoted context omitted.

Ha! Find me where I can buy it for $2000.

Yeah, how do people have these in their hands already? Everywhere I look is sold out.

It's sold out to the people who have these in their hands already.

Re: Nvidia's RTX 5090 power connectors are melting

#295

Post by ryao »

Sohcahtoa82 wrote: post #175
dcrazy wrote: post #135

Earlier quoted context omitted.

Most residential wiring is 15A except for bathrooms.

And kitchens. Otherwise, running your microwave, toaster, and coffee maker at the same time would likely trip the breaker. And obviously, the stove/oven is on its own circuit unless it's gas.

My kitchen has at least 2 120VAC circuits, which seems to avoid this.

Re: Nvidia's RTX 5090 power connectors are melting

#296

Post by zamalek »

tcdent wrote: post #285
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 lim…

"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.

Re: Nvidia's RTX 5090 power connectors are melting

#297

Post by ryao »

Kirby64 wrote: post #241
diggan wrote: post #217

Earlier quoted context omitted.

> I envy my European friends' 240v electric kettles ... do you not have electric kettles in the US? Foolishly, I thought this was a standard kitchen appliance all over the world, I've even seen it in smaller cities in Peru.

We do, but they’re limited to much lower wattage due to the outlet limits. A typical US kettle is 1100-1400W, and takes maybe 1-2 minutes to boil. Kettles in the UK are typically 2.5-3kW.

Amazon lists 1500W models:

https://www.amazon.com/electric-kettles/b

Re: Nvidia's RTX 5090 power connectors are melting

#298

Post by jrockway »

immibis wrote: post #272
Dylan16807 wrote: post #240

Earlier quoted context omitted.

It's not great. Dropping 5V makes power routing more complicated and needs big conversion blocks outside the PSU. I would say it makes sense if you want to cut the PSU entirely, for racks of servers fed DC, but in that case it looks like 48V wins.

There are already huge conversion blocks outside the PSU. That's why they figured there's no need to keep an extra one inside the PSU and run more wiring everywhere. Your CPU steps down 12 volts to 1 volt and a bit. So does your GPU. If you see the big bank of coils next to your CPU on your motherboard, maybe with a heatsink on top, probably on the opposite side from your RAM, that's the section where the voltage get…

Yup, exactly. The VRMs on my Threadripper board take up quite a bit of space.

Re: Nvidia's RTX 5090 power connectors are melting

#299

Post by xxpor »

rollcat wrote: post #242
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…

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?

Why should we reduce power draw? We live in an age of abundance.

Re: Nvidia's RTX 5090 power connectors are melting

#300

Post by Miraste »

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 spec may say it, but I've never encountered a USB-C cable that claims to support 240 watts. I suspect if machines that tried to draw 240W over USB-C were widespread, we would see a lot of melted cables and fires. There are enough of them already with lower power draw charging.
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