Another possibility which is more common in "normal" PC setups is a loose pin. The pins can come slighly loose. When the connector is seated the male and female pins have a weak connection. Poor connection = higher resistance. Same amount of current with higher resistance = more heat.
A lot depends on the specific GPU. I ran heavily overclocked (watercooled) quad 5970 rigs with no powered risers and never had an issue. The 5970 actually pulls very little power (<20W) from the PCIe slot so the load on the motherboard is less.
Topic: Whats it mean when you burn out +12V pins? (Read 2620 times)
I've wasted plenty of money myself on stupid little mishaps. 
Many of us learned it the hard way. Believe me, you're not alone.
Thanks for the tip! I'll try powered riser cards next time.
I never liked having the cards so close together anyway.
I feel like this.
I never liked having the cards so close together anyway.
I feel like this.
If you used powered risers that wouldn't of happened. You overloaded the 12V line that powers the pcie bus, so it melted the point with the most resistance. If you use powered riser cables you can spread that 12v so you aren't stressing one point.
This could be related to the maximum power draw of mobo. GPUs aren`t directly fed by PSU in full. PCIe slots are fed from PSU through mobo to. Too much and it looks like that.
Rig was a MSI 790FX-GD70 with 4x 7950 Sapphires.
PS is Seasonic SS-1250XM
Last time I measured the power draw at full load it was about 1100w.
It was cooled by me putting a box fan next to the whole thing. It seemed to work fine for a week.
Today I smelled smoke, and it continued to work perfectly fine for a few hours after that then finally just powered off and wouldn't power on.
Upon inspection I could see pins 10 and 11 on the ATX power connector melted and fused with the ports.
https://i.imgur.com/7jrD7qu.png
https://i.imgur.com/isYGK7F.jpg
Both of those are the +12V
I've never seen that happen on a normal system. What I'm here to ask is, is there something specific to mining rigs (its probably unusual for most people to put 4 GPUs in a PC and run them at max speed 24/7) that could cause this? Should I have bought a better motherboard or power supply? Or cooled it better? I'm not sure what to learn from this.
I tried googling around and one suggestion was the connection wasn't secure, but I'm pretty sure it was secure, that kind of connector makes it hard to have a loose connection.
PS is Seasonic SS-1250XM
Last time I measured the power draw at full load it was about 1100w.
It was cooled by me putting a box fan next to the whole thing. It seemed to work fine for a week.
Today I smelled smoke, and it continued to work perfectly fine for a few hours after that then finally just powered off and wouldn't power on.
Upon inspection I could see pins 10 and 11 on the ATX power connector melted and fused with the ports.
https://i.imgur.com/7jrD7qu.png
https://i.imgur.com/isYGK7F.jpg
Both of those are the +12V
I've never seen that happen on a normal system. What I'm here to ask is, is there something specific to mining rigs (its probably unusual for most people to put 4 GPUs in a PC and run them at max speed 24/7) that could cause this? Should I have bought a better motherboard or power supply? Or cooled it better? I'm not sure what to learn from this.
I tried googling around and one suggestion was the connection wasn't secure, but I'm pretty sure it was secure, that kind of connector makes it hard to have a loose connection.
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