New 1080 almost not working. (black screen, not even bios)

Mar 1, 2018
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Hey guys.

So just bought new MSI GTX 1080 8gb Gaming X to swap with my current Asus Strix 1060 6gb.

My specs:
CPU: Ryzen 1060x
Motherboard: Asus Prime X370-Pro
Ram: 2x4GB DDR4 corsair
Storage: 2ssd, 1 hdd.
PSU: Corsair CX450M
Monitors: Dell 2k 27 inch connected with DP cable + old LG 23 inch connected with DVI to VGA converter

My steps to swap card:

1. Unplug everything.
2. Remove old 1060.
3. Install new 1080.
4. Connect GPU with PSU. 8 + 6 pin (from one connected to psu cable)

So I first run the system and everything were smooth and amazing. Drivers updated automatically with GeForce Experience and I played Kingdom Come deliverance for an hour or so.

The next day I tried to do the same, system started normally I started the game, after 5-10 mins system frozen with a black screen and I reseted it.

So now, if I start the system screens are just black (normally I see motherboard logo and bios options on the second screen (23 inch, connected with DVI to VGA)) so not even bios is visible, but by other signs anything boots up properly on the background.

Sometimes when I unplug power / reset bios / take out GPU and put it back everything start alright, but after restart same happens (black screens).

Now I'm back with my 1060 and everything is just fine.

Any ideas?
(Also tried different cables, swapping dp with hdmi but nothing seems to work)
 


Smells like the PSU. 12V reading in BIOS?
 
Mar 1, 2018
2
0
10


I'm not sure about psu. My spec + 1080 wouldn't go beyond 400 in any case (not OCd). Also bizarre that the first time everything was alright while playing demanding game.