Interestingly, I've been playing around with my two 24" LED Apple Displays on my nMP and it doesn't seem to matter what TB ports I use to connect them, System Report always shows both of them connected to the GPU in Slot 2. See attachment. I wonder if this is the nMP's way of keeping one GPU dedicated for compute while the other one is dedicated to driving displays. Related to this... In this Apple KB article, it says... Here are the TB bus configurations... (taken from the article) I assume this is really for 4K display users since there's not enough BW on a single TB bus to drive dual 4K displays. I've got both my MDP displays connected to one bus at the moment and it's not a problem (although my displays only consume about 6Gbps at 1920x1200x32@60Hz). Anyone have any other theories or comments on the way Apple has implemented display routing to GPUs in this machine?