New build workstation (Supermicro 7048GR-TR) with two GTX 980-Ti cards, Windows 8.1 Pro 64-bit.
 
In Windows device manager both GPUs show correctly (NVIDIA driver version 10.18.13.53900 of 13 Nov 2015), but in Precision/OC etc. I can only see one card - what have I missed to get the second card available?
 
EDIT:  After repeatedly un-installing / rolling-back / re-installing drivers it eventually sprang into life!
 
Dave