i have two rx 480s and either one plugged in works fine by itself. they work fine solo plugged into either slot. but when i have both plugged in then windows startup stalls forever, literally it just sits there on the pulsating windows logo, it doesnt freeze as it keeps pulsating but it never gets past that screen.
if it makes a diff im running an msi 890fxa-gd70 with a 1090t and 20GB ram. the latest driver, ive unistalled and reinstalled them a few times now. 16.300.2311.0. ive swapped slots and tried every combo and its always the same.