News RTX 5080 power cable allegedly melts at PSU — Redditor reports another 50-series failure

[truerock]

They should just simplify the cables and use only a single wire.

Not a horrible idea. I think way back in the mists of old-timey electronics they were trying to spread the heat out amongst more surface area - having more smaller wires as opposed to one thicker wire.

Also, I think there is something about alternating current (not DC that is used inside PCs) where engineers got off on multiple wires per cable. Something called the AC "skin effect" I think

 

[truerock]

You're right. A blown fuse is basically a melted wire.

My Xmas lights have teeny-tiny little fuses in the plug to stop accidental overloading and short circuits.
Potential solution?

 

[Eximo]

Not a horrible idea. I think way back in the mists of old-timey electronics they were trying to spread the heat out amongst more surface area - having more smaller wires as opposed to one thicker wire.

Also, I think there is something about alternating current (not DC that is used inside PCs) where engineers got off on multiple wires per cable. Something called the AC "skin effect" I think

That applies to DC as well. A stranded wire can carry more current than a solid wire of the same cross section. Multiple cables is just a cheaper way to do that while not dealing with larger connectors where quality control is more of a concern.

 

[KidHorn]

Only if it is fused or has a circuit breaker. Not that common for there to be circuit breakers inside of low voltage electronics. Fuses are a thing, but they have to be able to handle quite a bit of power so they don't pop all the time.

PSUs are pretty dumb all things considered and as long as their internal protections aren't impacted they are perfectly willing to supply power. Most common designs now use a single rail, so you don't even have current protections that much.

23 amps is an insane amount of current going through a home outlet. My clothes dryer is on a 30 amp circuit.

 

[Eximo]

23 amps is an insane amount of current going through a home outlet. My clothes dryer is on a 30 amp circuit.

Not 23 amps at 120V or 240V AC, but 23 Amps at 12V DC (~300W or so)

 

[TJ Hooker]

Wouldn't a fuse blow or a circuit breaker trip if 23 amps was going through something designed for 9 amps?

PSUs don't do over current protection (OCP) on a per-pin basis. I don't think it's common to do even per-connector OCP. They typically do per-rail OCP (so total 12V current), or at most split 12V into a couple rails for separate OCP, with each 12V rail containing several of the 12V connectors.

 

[Peksha]

Not 23 amps at 120V or 240V AC, but 23 Amps at 12V DC (~300W or so)

It doesn't matter what voltage is used to heat the cable. Check your school formula. Only the current, cross-sectional area and specific resistance are important.

 

[TJ Hooker]

That applies to DC as well. A stranded wire can carry more current than a solid wire of the same cross section. Multiple cables is just a cheaper way to do that while not dealing with larger connectors where quality control is more of a concern.

That's backwards, a solid wire can carry more current than a stranded wire of the same size.

https://eshop.se.com/in/blog/post/stranded-vs-solid-wire-optimal-choice-and-reasons.html

 

[Eximo]

That's backwards, a solid wire can carry more current than a stranded wire of the same size.

https://eshop.se.com/in/blog/post/stranded-vs-solid-wire-optimal-choice-and-reasons.html

Yes, sorry. I always do that. The skin effect is there, but when comparing the same gauge, solid carries more current.

If you do only cross sectional area, meaning the stranded gauge goes up in size but is an equal amount of copper as compared to the solid, than the stranded performs better (more skin effect area)

 

[TJ Hooker]

Yes, sorry. I always do that. The skin effect is there, but when comparing the same gauge, solid carries more current.

If you do only cross sectional area, meaning the stranded gauge goes up in size but is an equal amount of copper as compared to the solid, than the stranded performs better (more skin effect area)

Skin effect doesn't apply at DC. Also, typical stranded wire doesn't do much for skin effect. Litz wire, where each strand is independently insulated, is used to mitigate skin effect.

 

[Eximo]

Hmm, I may have been mislead by my old electronics instructor. I have some reading to do.

 

[alceryes]

It could very easily be the PSU's fault if it wasn't sending the power equally on all of the pins and was sending power out of spec on one of the pins like der8auer saw.

Please explain how the PSU can decide which of the 12V pins to send more or less power to? All the 12V pins are connected to one contact inside to PSU. The PSU see one contact - it doesn't see the pins separately.

 

[sillysaxon]

I wonder how many of these folks have tested their home power to make sure they have a strong ground at their receptacles?
Mine had been painted and wasn't making much contact, which meant REALLY hot PC power cables!

 

[JTWrenn]

I think it is, but I would still like an explanation as to how it could be the PSU's fault.

The six 12V pins are connected to their receptacles inside the connector at the PSU and those receptacles are, in turn, connected or soldered to one supply contact. The PSU can't say, "Give this 12V pin more Amps and give this one less," It's one connector/pin/receptacle as far as the PSU is concerned.
What we are seeing (great example in der8auer's latest video) is electrical engineering 101. The path of the electric current on one or two of those pins has an overall lower resistance than other pins. It could be something as simple as the slightly shorter physical path (e.g. on pin 1) due to it being physically closest to the GPU PCB.

Doesn't that mean that the connectors on the receptical of the PSU could cause the issue? ie if the connections are not solid you could get one pin pulling more than another and a possible overload. Or simply that the pins are not in proper condition and there is no overload per say but rather just heat build up from a bad connection.

That was the whole idea the first time around right? Lots of power and the plug not in all the way. The same could happen on the other end right?

Honestly I think this is just a badly designed plug that is just too small per pin for the power. However that tight window could make the connection on either side need to be so near perfect that a defect in either socket could cause heat.

 

[alceryes]

Doesn't that mean that the connectors on the receptical of the PSU could cause the issue? ie if the connections are not solid you could get one pin pulling more than another and a possible overload. Or simply that the pins are not in proper condition and there is no overload per say but rather just heat build up from a bad connection.

That was the whole idea the first time around right? Lots of power and the plug not in all the way. The same could happen on the other end right?

Honestly I think this is just a badly designed plug that is just too small per pin for the power. However that tight window could make the connection on either side need to be so near perfect that a defect in either socket could cause heat.

Good, good. Now we're getting to what I believe is the crux of the issue - crappy design.

Yes, what you mention is entirely possible, but we don't see this with any of the other PSU cable connections do we? Aside from extreme outlier cases, we don't see 12V ATX cables regularly bursting into flames or EPS 12V turning into a puddle of plastic goo. We don't see SATA or fan 4-pin molex connectors popping inside the case like mini fireworks. Why? Because their rated wattage and safety factor are good enough to catch 99.99% of out of spec usage and less than ideal conditions (poor contact/high resistance).

This 12V-2x6 isn't even able to do it's rated 600W! (I think der8auer was showing 575W)

 

[Notton]

I wonder how many of these folks have tested their home power to make sure they have a strong ground at their receptacles?
Mine had been painted and wasn't making much contact, which meant REALLY hot PC power cables!

That's not how ground works in AC.
Ground for AC is to prevent electrocution when there's a short between live and exposed metal. Usually caused by faulty wiring in a metal lamp.

For DC, you don't want the live wire causing a short to ground, else you get the NZXT H1 recall.

 

[JTWrenn]

Good, good. Now we're getting to what I believe is the crux of the issue - crappy design.

Yes, what you mention is entirely possible, but we don't see this with any of the other PSU cable connections do we? Aside from extreme outlier cases, we don't see 12V ATX cables regularly bursting into flames or EPS 12V turning into a puddle of plastic goo. We don't see SATA or fan 4-pin molex connectors popping inside the case like mini fireworks. Why? Because their rated wattage and safety factor are good enough to catch 99.99% of out of spec usage and less than ideal conditions (poor contact/high resistance).

This 12V-2x6 isn't even able to do it's rated 600W! (I think der8auer was showing 575W)

Yup I completely agree. Tolerances are the crux of almost all of these issues. To me they are going backwards. Higher power and lower tolerances are just a bad idea especially for something being installed by an end user.

 

[Mr Majestyk]

Each of the 12V pins of the connector is connected to a single plane - they are one metal connector both inside the PSU and on the GPU. More amps will get pulled through the path of least resistance.

Because the safety margins of this connector design are so horrifically (erroneously) low, we are seeing the result of those limits being surpassed until physical failure. Pins that are only rated to carry 9A are seeing 23A+ going through them. This is the direct result of a flawed design and is in no way a failure of the PSU.

^^^This.

8-pin molex has 90% safety margin, Nvidia's proprietary crap has about 10% IIRC. So glad AMD eschewed it.

 

[Mr Majestyk]

That's not a terrible idea. Although you would need a transformer between the plug and card because you would need to go from 110v AC to 12v DC. Most home outlets are rated at 20a minimum, which is 2400w. More than enough.

We might need 3-phase for future Nvidia products. In Australia that's rated to 120A, so might be enough?

 

[JamesJones44]

That's not a terrible idea. Although you would need a transformer between the plug and card because you would need to go from 110v AC to 12v DC. Most home outlets are rated at 20a minimum, which is 2400w. More than enough.

This actually depends on local ordinances. 15a outlets are not uncommon, poor unsuspecting customers might also need to hire an electrician. Maybe Nvidia can roll electrician costs into the price of the 6090 😀

 

[palladin9479]

Wouldn't a fuse blow or a circuit breaker trip if 23 amps was going through something designed for 9 amps?

The circuit breaker is the metal connector at the PSU and card. Dead serious... they have zero protection while expecting over 600W worth of power to go down a small cable.

 

[palladin9479]

^^^This.

8-pin molex has 90% safety margin, Nvidia's proprietary crap has about 10% IIRC. So glad AMD eschewed it.

It's way more then 90%, the eight pin connector can take something like 2.2x the rated capacity.

 

[KyaraM]

I think it is, but I would still like an explanation as to how it could be the PSU's fault.

The six 12V pins are connected to their receptacles inside the connector at the PSU and those receptacles are, in turn, connected or soldered to one supply contact. The PSU can't say, "Give this 12V pin more Amps and give this one less," It's one connector/pin/receptacle as far as the PSU is concerned.
What we are seeing (great example in der8auer's latest video) is electrical engineering 101. The path of the electric current on one or two of those pins has an overall lower resistance than other pins. It could be something as simple as the slightly shorter physical path (e.g. on pin 1) due to it being physically closest to the GPU PCB.

The way you latched unto a SINGLE guess/idea/question I put forward, out of several, and the way you act about it, make me extremely disinclined to talk to you about it further. I was simply considering manufacturing defects on all sides, including Nvidia, and there was no reason to get patronizing about it. Looking around the comments on other topics here about this issue you MIGHT have noticed I was even the first person to bring resistance up originally, but hey.

 

[DS426]

Folks, again, it really just comes down to a much smaller margin of forgiveness in the ATX 3.0 and 3.1 standards, specifically regarding 12VHPWR and 12V-2X6. Yes, better cable quality and better PSU's and lower-power nVidia flagship cards might have reduced the number of these cases, but this will continue to happen under voltage is raised above 12VDC and some other fail-close mechanisms are built-in.

The fact that a 5080 can fail at a 360W TGP shows it's more than just a thirsty GPU problem; Radeon RX 7900 XTX has a TBP of 355W but with no issues on melting connectors.

This obviously caught nVidia off-guard as this wasn't a problem on the 3090 Ti because its 12V handling was engineered properly; nVidia dropped the 12V input from three separate shunts (where one failing would shutdown the GPU) to all current coming in over a single shunt. Buildzoid has an interesting video on this:

View: https://www.youtube.com/watch?v=kb5YzMoVQyw


Even when you have low-quality cables, this should result in system stability issues, NOT burned connectors and wires. This illustrates a lack of robust standards and/or engineering (4090 and 5090's 12V design regression is presumably for cost-savings) on electrical devices on either end of a conducting path.

 

[truerock]

That applies to DC as well. A stranded wire can carry more current than a solid wire of the same cross section. Multiple cables is just a cheaper way to do that while not dealing with larger connectors where quality control is more of a concern.

Interesting...

I have a vague recollection of a datacenter project where we were thinking of having one big power supply for each row of server racks. If I remember correctly, they were going to use something that looked like a copper bar to transmit the DC electricity down the row of server racks.

***************************************************************
Copilot:
It sounds like you're recalling a setup using busbar systems for power distribution! Busbars are thick strips of copper or aluminum used to conduct electricity within a data center. They're often employed to distribute power efficiently across multiple server racks in a row. This setup can help reduce power losses and improve reliability by providing a robust and centralized power distribution method.

TrueRock:
Why copper bars instead of stranded wire cable?

Copilot:
Great question! There are a few reasons why copper busbars are preferred over stranded wire cables in some data center applications:

Efficiency and Performance: Copper busbars offer lower electrical resistance and can carry higher current loads more efficiently compared to stranded wire cables. This helps reduce energy loss and improve overall performance.

Heat Dissipation: Busbars have a larger surface area, which allows for better heat dissipation. This helps keep the system cooler and enhances reliability, especially in environments with high power density.

Space Optimization: Busbars can be designed to fit compactly within server racks, making efficient use of space. They eliminate the clutter of multiple cables and provide a neat and organized power distribution solution.

Ease of Maintenance: Busbars are easier to maintain and troubleshoot since they are mounted in a fixed position. Identifying and rectifying issues can be quicker compared to dealing with a bundle of cables.

Scalability: Copper busbars provide a modular approach, allowing for easy expansion and reconfiguration as the data center's power requirements change.

In short, copper busbars offer a combination of efficiency, performance, and practical benefits that make them a reliable choice for power distribution in data centers.