Yeah I need to connect all displays to the primary card as well, though it's been like that for as long as I can remember. That is strange. I wonder if it's related to recent Win 10 fullscreen optimizations behaviour -- designed for all those nutjobs that want fullscreen acceleration in Borderless Windowed mode just so they Alt-Tab mid-game instead of, I dunno, playing the game. I mean.. are you playing the game or not playing the game? I digress. SLI by definition needs Fullscreen Exclusive (as do other features like DSR). With FS optimizations on it absolutely fucks around with games. E.g for both Creators updates I had to ensure FS optimizations are disabled globally, otherwise I get behaviour like stuttering in-game (people with single cards are seeing this too), odd loads on SLI, and crap like a game starting windowed bordered even though its setting in-game is 'Fullscreen Exclusive' and needing to re-set the settings every time. procreating debacle Microsoft. This fixed all problems though: Regedit: Computer\HKEY_CURRENT_USER\System\GameConfigStore Set: GameDVR_FSEBehavior to 2 GameDVR_FSEBehaviorMode to 2 Reboot. I don't know if it will help, but it can't hurt trying. I'm on 1803 now and every game is smooth as a baby's butt again with and without SLI.