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So I've had my 3x7950 rig up and running for just over a month now, everything has been running real smooth. But a couple of days ago, Reaper started becoming totally unresponsive after running for about 2 or 3 minutes causing the cards to power down and windows to hang.

Thought it might be a driver issue, uninstalled/reinstalled gpu drivers/SDK even reinstalled windows. Nothing helped, so I figured it must be hardware related.

Discovered what the problem was today after testing the individual cards - I had 2 of the cards powered with the proper PCIe power cables (all good), and the third powered with Molex adaptors - I had both the 6 pin and the 8 pin adaptor connected through a single peripheral cable to 1 socket on the PSU. Derp. And the plug had half melted itself into the PSU. Shit.

Luckily no damage was done to the card and the PSU still seems to be working fine. I assume too much current was going through the cable.

I've got the card running on a separate PSU now to be safe. Question is, would it have been OK if I had used 2 peripheral cables instead of 1? so 1 cable for the 6 pin power socket and another cable for the 8 pin? I'm using a Corsair AX850 PSU.
Any advice would be appreciated, cheers.

off-topic (probably related?), but i had some 16 gauge extension cord that had an unfortunate melting incident.  i use all 12 gauge cords now (power supply + extension cords)

on-topic, i imagine the pci-e connectors are 18 gauge wire,  the molex maybe just 20 gauge ?  does it say 20 awg on it?     

the PSU itself should be able to handle 3 cards

yeah well the molex adaptors are 18 gauge, the connecting cable that they're plugged into doesn't say (it's one of those peripheral cables with 4 plugs along the length of it, kinda like christmas lights)... You're right, the PSU should be able to handle the power...

You see ideally I want the single PSU powering the 3 cards so I can use the extra PSU in another rig.

In theory, splitting the power drain of the GPU between 2 molex/peripheral cables instead of 1 should split the current load, resulting in less heat and meltage, right? It makes sense in my head but I'm a bit wary - don't wanna end up with a pool of very expensive molten plastic  :D

Which PSU?

Just get a PSU that has cables with the correct connectors in the first place, so you don't have to use shitty adapters and guess about this kind of stuff.

Basically I want to power 3x7950 cards with my corsair 850AX, just wanna know if it will be safe to power a single card through 2 periph/molex cables instead of doing it through the single periph cable (which melted the PSU connection plug)  :-\

Well it's a decent psu,  but it only had 2 standard (double) PCIe cables bundled with it (which I used for 2 out of the 3 cards). I just think i made the mistake of routing both the gpu power connectors on the 3rd card through a single periph cable instead of using two cables. Will using 2 cables work do you think?

Consider yourself lucky. What you had was a fire waiting to happen.

Yes I know it was dodgy, ran for a month without issue though.

Do you have advice as to whether using 2 cables instead would be safer then Mr ROSPA??

this is why i dont do molex at all for gpus anymore. PCI-E plug splitters all the way.

http://www.ebay.com/itm/290778077889
http://www.newegg.com/Product/Product.aspx?Item=N82E16812198018

I'd recommend the first one over the second one as the wires seem to be a smidge thinner, and dispersing the load in parallel instead of series is a lot safer and stable. Mind, I'm using the series ones because I got them cheaper from newegg and they work great, but the ebay ones will be safer and capable of a higher load.

Cool nice one, think I might get a few of them at that price. But just to clarify, there would still be a single 6 pin PSU plug connecting both GPU connections (8pin+6pin) with these, which is where my problem occurred (melted 6pin plug in the PSU).

Would it not be better to do: 6 pin from GPU -> 6pin socket on PSU, and a separate 8 pin from GPU -> different 6pin socket on PSU...?

your topic says molex adapter. thats the 4 pin to 6 pin. we are talking about splitting a pci-e 6 pin into 2 pci-e 6+2 pin. I have a 51 gpu farm and I use many of these adapters. they worked fine when I ran my 7970 at stock volts (almost 300 watts!) through these adapters. I also daisy chained them for a psu that only had 4 pci-e plugs.

yeah, i prefer to use those as well.   only on one system do i use those molex to pci-e craps