Why do I get "Error: Node instance "serdes" instantiates undefined entity "<core name>_serdes"" when I compile the PCI Express SoftIP in Gen1x8 mode for Stratix IV GX or Arria II GX.

Due to a bug in the PCI Express® IP, the GUI incorrectly allows users to select Gen1x8 configuration SoftIP when targetting Stratix® IV GX or Arria® II GX.

Both Stratix IV GX and Arria II GX devices only support the SoftIP implementation in Gen1x1 and Gen1x4 mode.

SoftIP Gen1x8 mode is not supported by these devices. Hence the IP fails to generate correctly, which causes the compilation error.

To workaroud this issue simply:

• Generate the SoftIP in either Gen1x1 or Gen1x4 configuration.
• Use the PCI Express HardIP Gen1x8 mode, which is supported in these device famlies.

This issue will be fixed in a future version of the Quartus® II software.