PSU melted to motherboard, what drew the power?

ubersonic

ubersonic

ubersonic

Soldato
Joined
26 May 2009
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22,181
Hey, was playing a game on my secondary rig and the system shut down and wouldn't turn back on. While removing components to figure out what was junked it soon became apparent it was the PSU (and the motherboard /grr) as the ATX connector had melted into the socket.

What do these pins power? Was this a case of the board drawing too much and melting the connector or was it an issue with the PSU?

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Big Frank said:
What spec is your system including psu wattage?
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Off hand (it's a secondary system I game on while my main system is doing looong workloads) IIRC it's:

CPU: Intel i7 4930K
MB: ASUS Rampage IV gene
RAM: 8GB DDR3 1600MHz
GPU: Crossfire 8GB RX480s
SSD: 256GB Samsung 840
PSU: 750W EVGA GQ Modular
 
Both of those pins are 12v1, that would suggest to me that either the connector wasn't seated correctly, or the board has failed. Doubt it's anything to do with the GPUs.
 
Managed to get to the bottom of it guys, it was the GPUs >.>

As a stop gap to have something to game on until my main rig finished it's workload I dropped them into an old Dell Precision T5400 workstation and everything seemed okay, but as soon as I got into some heavy gaming the system switched off and threw light codes, turns out it's a safety trip for out of spec power. And that's where the problem lies, the reference RX480 cards don't conform to the PCI-E spec (they draw too many amps from the PCI-E slot) which is something I didn't know, when used in a consumer board as opposed to workstation they will eventually kill it (and the PSU cable) over time.

Due to the design flaw AMD apparently released new drivers that cause the cards to draw more from the PCI-E cable and less from the slot, and I was using newer drivers, but they're still right on the limit and if you run in crossfire you're expected to toggle a slider in the drivers to further limit the cards power consumption, sadly I was unaware of this as were the many others who have fallen victim to this ticking time bomb.
 
That’s absolutely disgusting. I’d be contacting them for compensation.

‘Out cards will damage your computer unless you update drivers and know to toggle a slider’ is not a valid excuse.
 
WantoN said:
That’s absolutely disgusting. I’d be contacting them for compensation.

‘Out cards will damage your computer unless you update drivers and know to toggle a slider’ is not a valid excuse.
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It is definitely worth contacting them directly to see what they have to say for themselves, they might offer you something.
 
I would have thought the 8 pin eatx would take care of that load, they're good for 200watts on their own. I can't image the board pulling all of the pcie power from the main 24/28 pin plug. Something doesn't feel right. I know this blew up when it was discovered but I remember it ending up being a lot of talk and very little substance and as I recall they weren't the only cards to pull 75w+ from the pcie a lot. Weird.
 
The RX480 is not the only card that dose this
But it is a budget card that is used in budget computers
It should not be a problem with a single card
With 2 cards the selection of the motherboard and power supply will affect the outcome
As the 24 pin powers the PCI express slots and there are only 2 pins for this job
The spec on the cheaper 24Pin plugs is 6Amp and this is the problem
A 75W power draw will request 6.25Amps minimum from the 24 pins per cable
It is out of spec by design not entierly AMD`s fault but they are not helping by not considering user equipment
As a reference, there are 24 pin plugs called Plus HCS Terminals and they are rated for minimum 11Amp but cost more

In your case the power requirement from the 24 pin has overwhelmed the plug resulting in thermal runaway
A better plug, power supply`` will not melt

The Dell workstation has a multirail design with an 18Amp limit per rail
You need the schematic to see with components are sharing the rails
The safe shutdown might be a power limit on the individual PCI express slots like 35W

But do contact AMD and see if they are willing to help
Otherwise do you have warranty for the PSU or motherboard?
 
james.miller said:
I would have thought the 8 pin eatx would take care of that load, they're good for 200watts on their own. I can't image the board pulling all of the pcie power from the main 24/28 pin plug. Something doesn't feel right. I know this blew up when it was discovered but I remember it ending up being a lot of talk and very little substance and as I recall they weren't the only cards to pull 75w+ from the pcie a lot. Weird.
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The 480 has pretty jank power management in general (see the way they cheaped out with the common/ground) - not really a problem with a single card but completely possible to kill a board/PSU with them in Crossfire or even just two of them not in Crossfire.

They are I believe the only line of cards to pull power from the PCI-e slot in the manner they do - the behaviour of other cards even with high slot draw is different - someone did a lot of testing at the time with an oscilloscope and amp meter, etc.

EDIT: I suspect in this case it was a loose connection compounded by the above that caused the problem though - a lot of people don't put the ATX connector in that end with the additional 4 pin bit correctly.
 
james.miller said:
I mean the board, it has an 8 pin eatx socket.
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Ahh, AFAIK that powers the CPU not the PCI-E slots.


tres_kun said:
The RX480 is not the only card that dose this
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Actually it is, AMD never screwed the design up so much before or after.


WantoN said:
‘Out cards will damage your computer unless you update drivers and know to toggle a slider’ is not a valid excuse.
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Apparently they thought it was lol.

In this driver we’ve implemented a change to address power distribution on the Radeon RX 480 – this change will lower current drawn from the PCIe bus.

Separately, we’ve also included an option to reduce total power with minimal performance impact. Users will find this as the “compatibility” UI toggle in the Global Settings menu of Radeon Settings. This toggle is “off” by default.
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This is what really irks me about it, they know they screwed up, they know their product has a design flaw, they add a fix to new drivers, and they have it disabled by default /facepalm.
 
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You would think people who buy two cards for xfire, would be knowledgeable enough to have heard of the issue, and took precautions. This was huge deal blown out of the water by press when Polaris launched. And when I say huge it was borderline out of proportions. So you would think that those who consider two card would know about it, and not come back 2.5 years later asking why their motherboards are melting :)

P.S. I'm not defending AMD here, just curious of the circumstances which prevented non average joe to keep using 2 card and not knowing of the issues those cards had :)
 
muziqaz said:
You would think people who buy two cards for xfire, would be knowledgeable enough to have heard of the issue, and took precautions.
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The design flaw wasn't widely known about at launch, there are no precautions you can take aside from not using two cards or using a 3-4 card motherboard. AMD still lists Crossfire as a supported feature on the RX480's web page with no mention of the design flaw or the inherent dangers.
 
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