There were some modifications to the SRIO v5.5 Core (released with ISE Design Suite 12.1) that should relieve the timing difficulties for most cases. In some rare instances, however, this timing constraint may still fail which may require advanced timing closure techniques in order to meet timing. In particular, Area Groups that are large enough to constrain the Core to a particular area have helped improve timing, as well as using different cost tables (-t option in Map/Par) and/or SmartXplorer.
04/27/2009 - Initial Release
06/30/2009 - Updated fix schedule
04/08/2010 - Updated fixed version