When using Block Level Incremental Synthesis (BLIS) flow with FPGA Express in Foundation ISE, all design netlists will be rewritten, even if the source for the given module has not been changed. While the timestamp on the netlists will be updated, unchanged modules will not be resynthesized, and therefore the BLIS flow will work as desired with the exception of the fact that the timestamps on the EDIF netlists will be updated (ie, the contents of the EDIF file will remain unchanged for those blocks whose source has not changed).