I've set this up before. How many video cards are you trying to use to connect these monitors? I've always had it just work if you are only using one card. I

I've set this up before. How many video cards are you trying to use to connect these monitors? I've always had it just work if you are only using one card. In the past I've had to invoke xrandr with the --setprovideroutputsource flag (or was it --setprovideroffloadsink ?) to get multiple monitors to work with multiple video cards. Note, this only works with the open source drivers and you must be using an X server that supports randr 1.4.