I've got 12 of the same memory (hynix) 580s. First 6 work like a dream, flashed them all with the same bios and it worked perfectly.
On to the next rig, it plug everything in and it works straight away, detects all 6 cards.
I flash the cards with same bios as before (same memory, same brand, purchased together) and now one of the pcie slots fails to show up in windows.
The motherboard I'm using (tb250-btc pro 6 gpu ver) has a post screen that shows if your pcie slots are working, faulty or not being detected.
The motherboard post screen shows everything to be working fine, but windows won't detect one pcie slot since the flash.
The riser/gpus work perfectly on all other pcie slots, it's just this one that windows has decided to forget.