Dear Max,
We have one working design with ll_temac ethernet and dual MCBs for LX150.
It is on the new trenz SVN and was developed with EDK v12.
Lately we developed similar with AXI architecture.
The major problem at the beginning was pll placement and pll lock signal routing.
As I remember it uses one PLL for 625MHz clock generation. The lock signal from this pll needs to be routed directly to MCB plls.
You can take this design for a reference.
Maybe you have also some problems with IOSTANDARD definition for unconstrained MCB signals (ZIO, RZQ).
Best regards,
Ales