For asynchronous links, users should modify the PMA_RX_CFG setting in the GTX wrapper file.
Edit the gtx_wrapper_v6.v[hd] file found in the generated core's source directory and change PMA_RX_CFG to be 25'h05CE049. For more information on clocking, see (Xilinx Answer 18329). Revision History 01/18/2012 - Updated; added reference to 45723 12/24/2010 - Initial Release
Note: "Version Found" refers to the version the problem was first discovered. The problem might also exist in earlier versions, but no specific testing has been performed to verify earlier versions.