Why do the post-synthesis simulation results vary from the behavioral simulation results in 2014.1?
This is a known issue with the G.975.1 EFEC I.4 Encoder/Decoder v1.0 (Rev. 4) in Vivado 2014.1.
This issue can be worked around by generating and synthesizing the G.975.1 EFEC I.4 Encoder/Decoder v1.0 (Rev. 3) using Vivado 2013.4.
This issue will be fixed in a future release of Vivado Design Suite.