Hi i have 2 1080 SC in SLI.
 
Ran bios update and screens all went black. waited approx an hour, then just rebooted comp.  And now my system only detects the intel HD520 graphics on motherboard. The two 1080s are not detected.
Tried redoing bios update, says it passed, but still nothing. Anything to test, or do i need new cards?

Welcome to the Forum SapphicNeko
 
Did you disable SLI before you updated the Bios?
Remove the SLI Bridge and then Reset your MB Bios, pull battery or what ever way you do it and then see if they show;
1) in the Bois
2) in the OS

Redid update without sli bridge. No difference. My motherboard Bios says I have Nvidia GPU running at x8 native in slot 1 and 2.

Try updating the cards one at a time. Take the other completely out of the system when updating the other.

Then they're not "not detected" by your sys as you say bios sees both.
Sounds like something borked in OS.
Cards seen in device manager?

Sajin
Try updating the cards one at a time. Take the other completely out of the system when updating the other.

For stuff like this I am glad I can turn off my PCIe Lanes.

Can you try to reinstall the driver?

Ok. I tried updating drivers first. It sat a very long time on detecting system, but they installed. Rebooted, and still same issue.
Then tried Saijins suggestion, took one card out, booted up and suddenly it saw that card fine. So i shut it down again, swapped the card with my other one, booted up, that card worked too.
So i put the first one back where 2nd was. Put in the SLI bridge, and now everything seems to work fine again.
 
Thanks lovely people for the help, <3 you.

 
Glad you got it fixed.     

SapphicNeko
Ok. I tried updating drivers first. It sat a very long time on detecting system, but they installed. Rebooted, and still same issue.
Then tried Saijins suggestion, took one card out, booted up and suddenly it saw that card fine. So i shut it down again, swapped the card with my other one, booted up, that card worked too.
So i put the first one back where 2nd was. Put in the SLI bridge, and now everything seems to work fine again.
 
Thanks lovely people for the help, <3 you.

I'm too late to the party but had the same sort of issues installing 1060s (No bios update though, DDU, clean driver install, the usual ritual) Install both and boot- No GPU detected (No SLI involved, not supported)  remove one and start up> GPU seen> install 2nd> boot up> GPU seen  *shrugs* been fine since.