Version Found: MIG 7 Series v1.8/1.8.a
Version Resolved: See (Xilinx Answer 45195)
The MIG 7 Series DDR3/DDR2 designs have internal signals that include both KEEP and MAX_FANOUT attributes applied to ensure proper implementation and successful timing.
In some cases (2:1 designs with greater than 64-bits, running at the max data rates), this causes the MAX_FANOUT to not be accepted and timing violations to occur.
If timing violations are seen related to signals that have both KEEP and MAX_FANOUT applied, please open a WebCase for assistance with timing closure: