Could be a listing for a not sold at retail. Some AMD FX chips carried an “FX-” prefix with 4, 6, or 8 cores, all 64-bit. “64-bit exclusive” is redundant — all x86-64 CPUs from 2003 onward run 64-bit OS.
Before generating the bitstream to program the FPGA, simulate your design to ensure it behaves as expected. xf a2012 64bits exclusive
: Indicates it is the version specifically for 64-bit Windows operating systems. Could be a listing for a not sold at retail