Troubleshooting overheating issues with my cracking rig

Hi everyone,

I'm continuing the discussion started in this thread: https://hashcat.net/forum/thread-5524-po...l#pid29785
In it, I described having overheating issues with my 4x Radeon R9 290X from XFX setup. I was advised to use reference nVidia cards instead.

So here I am, back with a pair of GeForce GTX 1080 Founder's Edition from PNY, facing the exact same overheating issues: when the computer case is closed, Hashcat shuts down after 10 minutes of cracking. Here is an updated picture of the rig:



Any idea what I could do to fix this? It's very frustrating to buy very expensive GPUs and be unable to use them