Burned out 12 V wires from PSU

[turbogiant76]

I have a rig I have been running Hashcat on pretty much 24/724/7.  It turned itself off yesterday and after looking at the components, I noticed the two yellow wires for the 24 pin connector had melted through the plastic sheath as well as melting the plastic pin connector.  Looking up a diagram of the 24 pin connector shows these are the 12 V leads.

I am running two GTX 980s and a was using a Corsair 750 HX PSU.  Was this just too much of a load for the PSU?  I would think it wouldn't affect it like this since the cards should only pull 75 watts through the 24 pin connector via the slot, and get the majority of their power through PCI-E cables.

I have ordered a EVGA Supernova 1200 P2 PSU to replace the bad unit.  Will I be good to go or will running the cards like this cause the same problem.  I was considering running HC at -w 1 instead of -w3 to decrease the load, but this will slow it down.  Is this a good idea to do?

[epixoip]

Hmm... It's interesting you'd have this problem with Nvidia GPUs. When I first started reading, I thought for sure you'd say you were running 6990s or 290Xs or something.

GPUs do tend to have a bad habit of drawing > 75W through the PCI-e slot, that's why gaming motherboards typically have the molex/sata power connector by the PCI-e slots to provide them with supplemental power. And before that, EVGA had a little card that you plug into a free PCI-e slot to provide additional power.

But this makes no sense with GTX 980s. You'd have to be drawing > 225W each for them to want to draw more than 75W through the PCI-e slots, and I don't think it's physically possible for the card to draw that much power. Unless you have OEM design cards that are designed poorly and thus are drawing most of their power from the PCI-e slot instead of from the PCI-e cables... So I guess I should ask, are these reference design or OEM design cards?

[royce]

I'm not as much of a power expert as others in the forum, but here's my take. Max power for 980s is 165W. Even if you were doing password generation on your CPU or something, assuming max 350W for the rest of the board running at full tilt, I would expect your power supply to have been OK for the task. What's the motherboard and CPU?

I would definitely expect a 1200W PSU to be more than enough. I have 6 970s in a single chassis, and unless I'm running something on the CPU as well, I only pull 1050W from the wall with all GPUs engaged, and only 105W at total idle.

You may want to get a Kill-A-Watt so that you can measure power consumption yourself. I find it helpful to baseline with no load and no GPUs inserted, peg the processor and measure that, install the GPUs and measure GPU-only draw, and then measure draw with both CPU and GPUs pegged.