Hello,

I've bought 6x of this MSI r9 280X card on Amazon.
http://www.amazon.fr/MSI-GAMING-Graphique-Radeon-PCI-Express/dp/B00GSIFMB0/

I can't manage an incredible noise like a few mining rigs I have seen in here with 20/30+ cards on a plastic crates or ingenious systems like those, but my idea was to create a lot of "strong computers" that I could put at many places I have access to to manage and mitigate heat, noise, and power hazard.

So my first idea was too put 3 GPU (of those) per "computer".

I bought a Corsair Carbine 540 with a Corsair RM1000 1000W PSU
This one : http://www.amazon.fr/Corsair-Boitier-Carbide-Series-CC-9011030-WW/dp/B00D6GINF4 which has a nice airflow system.

And as for the MB I bought this one Gigabyte 990FXA-UD3 :
http://www.amazon.fr/gp/product/B00545BZOG/ref=oh_details_o02_s01_i03?ie=UTF8&psc=1

Now my issue.
I tried with only two cards for a start instead of 3, I installed BAMT 1.3 on a USB stick, everything went fine.

But soon, I realized my GPU#0 was starting to have a higher temp than GPU#1.
At first it was 1 celsius degrees, after a couple of minutes...
GPU#0 was ranging between 93/95+C (fan at 100%) and an awful noise !!!
GPU#1 was ranging at 70/75C (fan at 70/85%)

I immediately thought that it was because the cards were too close from each other, so I put GPU#1 at the bottom of the motherboard, leaving a good space between those.
It helped, but the difference is still the same... GPU#0 is now 85/90C, and GPU#1 is 65/70C.

I've tried to tweak the settings with cgminer, to lower the core, etc..etc.. it helped a bit... but GPU#0 is still at over 80C (with a slower hash rate).

I'm really worried having a card that could boil water while mining, especially when the other seems fine.

Since I have bought 6 of them, I thought it might be a wrong/defective card... so I removed it... and placed a new one instead.... exactly the same behavior (minus 1 degree better).

That's where I'm stuck now.

What could explain such a large difference ? Is it because the GPU is close to the chipset at this spot ? If I underclocked would it really help the matter (at same clock it should roughly act the same) ?

What should I do for you ?
Besides mining, those 2 cards could be inside a gamer chassis, and why would they act like this ? If I put 3 of those, the chassis would be on fire.
Is the 280X a bad choice ? Is this MSI a bad choice and other brands are fine ?

I'm totally in time to return everything to Amazon, so I'm open to everything... my only constraint is to keep them inside a chassis (and ideally 3 of them to maximize the capacity), so your feedback is welcomed

Thanks a lot guys !