Some systems will use a custom parsing engine to parse the bitfile header information. These systems may encounter problems when a V-4 .bit file from 9.1.02 is loaded.
Additions made to the header of the ".bit" file in Service Pack 2 for V-4 devices added extra pad words to the ".bit" files to account for necessary padding when SelectMAP32 is being used at fast speeds. These changes have been found to cause problems for some customers parsing the .bit file header information at a system level.
In the 9.1.02 version of the software, all V-4 devices will have 7 extra pad words added to the bit file before the sync word.
In the 9.1.03 versions of the software, these changes are made only when the CONFIG constraint is set to use SelectMAP_32. The default bitstreams will not have the additional padding.
Xilinx does not intend to change the Virtex-4 bit file header format in any further releases of the software.