Are devices real or fake?
Can I tell if devices are counterfeit?
If the devices are not purchased from an authorized distribution or sales source (even if the Lot Code is correct), Xilinx cannot guarantee that the devices are real.
It is also possible that they are real devices but might not have been handled correctly, meaning the functionality or reliability of the devices could have been affected.
Therefore Xilinx cannot support devices not purchased from an authorized source.
In addition to not supporting devices from non-authorized sources, Xilinx cannot assist in determining if the devices are real or fake.
For the list of Xilinx authorized distributors see: http://www.xilinx.com/about/contact/authorized-distributors.html
All Xilinx parts are covered by this answer record.