PCI express compiler IO signals

Just make VIRTUAL_PIN assignments to those PIPE signals. VIRTUAL_PINs won't take up real pins on the device. Those signals are provided primarily to allow you to simulate your system bypassing the transceiver which should speed up the simulation. (Caveat: I think the VIRTUAL_PIN assignment works, if it doesn't then create a wrapper around the top level of your SOPC Builder system that leaves those PIPE signal outputs unconnected and drives the inputs with 0's.)