2 8x slot
1 4x slot
i don't believe there is enough bandwidth in a single TB port to support full 16x worth of bandwidth. rocket and sas cards only need a 8x slot. generally only gpu's really need 16x slots.
I've seen demos at NAB with the same magma I have with sas card to a 8 bay raid, with rocket and I/O card. it was downloading at full speed, and transcoding at near real time all at the same time, and could still play out of the i/o card with no hiccups. the slowest portion was the actual download from the redmag.
cards don't suck up all the bandwidth at once, it takes what it needs, a lot of the time it's nowhere close to what the maximum potential of the slot even has. There's a lot of play room to be had.