Recently got a P4080PCIE. Also purchased a Dell T5810 to host it. The x86 drivers just hang the kernel when loading (on any of CentOS6, Ubuntu 12 LTS, Ubuntu 14 LTS etc etc). So after a lot of hair pulling, I finally tried putting the card into an old PC, and voila, the drivers build and load no problem.
So my question is, how can I tell ahead of time if a motherboard will be compatible with the P4080PCIE? The Dell has PCIE gen 3 x16 slots, which are supposed to be backward compatible with the x8 gen 1 of the P4080PCIE, right? So what gives?