Hello,
the x-bar refers to the way the module is connected to the backplane of the Catalyst 6500. On the 6500, fabric-enabled modules and x-bar enabled modules are synonymous. What this is referring to is the attachment of the card to the backplane. Legacy modules will have a bus connection, while fabric-enabled or x-bar enabled modules have a connection to the backplane via a switching fabric also known as a cross-bar switch fabric.
HTH,
Georg