When you instantiate the Stratix® IV GX transceiver in PCI Express (PIPE) x4 and x8 configurations for Gen2 data rate, the ALTGX MegaWizard® Plug-in Manager provides the
rateswitch input port that is four bits and eight bits wide, respectively.
Altera has identified that asserting the
rateswitch port performs the rateswitch function when you simulate the above configurations. The remaining bits of the
rateswitch port (
rateswitch[7:1] for PCI Express (PIPE) x8 configuration and
rateswitch[3:1] for PCI Express (PIPE) x4 configuration) are not functional.
Workaround: Altera recommends that you connect all the bits except
rateswitch to zero.