Andreas
this image was made by me some time ago because what i did not understand why they dint use the 3th pcie controller of the P50xx and you explain me so,me post ago.
for them was best made two different board one for 5020 and one for 5040 put less slots and dont use pcie-pcie bridges and use the 3 pcie controller im sure like this the machine will be have all better.

first and second square on the second controller are pcie-pcie bdridge on lshw on linux i sow exactly this but i was hoping was not like this.
If i will have time i will go in my mancave where is my x5000 (i dont turn on it from 1 month)
and will copy and past the log of it just for have better vision of everything.