I bought a gtx 970 (GV-N970IXOC-4GD). I have a cintiq 21 ux display that uses dvi-i port and a samsung display that uses HDMI port. When i turn on both displays the cintiq (dvi-i) port always in "out of sync" state while samsung (hdmi) is in the normal state (turned on).
I solve the problem buying this type of adapter (dvi to display port)
for the cintiq monitor. Now i can use the two monitors. One in the display port and the other in hdmi port.
Hope that help guys!
Francisco