Michel,
ES = "engineering sample"
This is what we call parts BEFORE they are qualified for production.
In some cases, ES parts are completely identical to the final production, and in other cases, they are not identical (they have known bugs or problems we call "errata").
CES = "commercial grade engineering sample" (it has a speed grade)
Go look for V5 errata at:
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to find the exact differences.
If you have questions about any of these errata, please contact your distributor or Xilinx FAE.
We sell ES parts to customers early in order to give them a head-start on their design and debugging (over their competition).
The risk of purchasing an ES part, is they may have bugs (known, as detailed in the errata, or as of yet unknown, as all testing may not be complete nor all test programs in place). If the parts have bugs, there is no warranty (they are non-returnable, non-refundable). The normal warranties do not apply to an ES part.
As an example, ES parts are never accepted for a "RMA" (returned merchandise authorization) or for F/A (failure analysis).
It is recommended that ES never be used for production product. If used for production product, the purchaser must accept all of the risks, as Xilinx has stated these parts are not intended nor recommended for production product.
This is pretty standard practice in the industry, and is not unique to FPGA technology either.
Austin