Oups, sorry… Indeed, you are right Alex, this board has 1 GB
<http://www.club-3d.com/index.php/products/reader.en/product/radeon-hd-6570-coolstream-edition.html>

Thanks again for the clever explainations.

Thus, it was my last guess… Is there anything else I can do to find the origin
of this issue?

Sincerely,
Benjamin.