I am baffled as this has now happened twice to me. I have an HP z840 workstation with 2 CPUs installed. Of the 7 PCIe slots on the motherboard, I had 1-6 populated with devices, running fine for weeks. I go to install a device into the bottom (slot 7) slot, I now get no boot. No beeps. Just 30 seconds of fans before shutdown.
This happened to me once before, I didn't connect the dots then, and figured I had a faulty motherboard. I replaced it, worked fine until I tried the bottom slot again, now same symptoms.
I reset CMOS button, no change. Power supply shows green button.
I just cannot fathom that this board destroys itself upon use of the bottom slot. Does anyone understand what is happening?