Yes. Linux came before AMD64, but that’s irrelevant. Corporate UNIX was more popular than Linux in the 1990s. AMD64 launched with the Opteron in 2003. In 2004, it was making AMD hundreds of millions per quarter and it was beating both Sun and Intel in server sales. Intel and HP were trying to push Itanium at this point, and Itanium was performing quite poorly. By 2004, AMD Opteron was also doing better than IBM Power. AMD was was crushing it.

EDIT: To give an idea of AMD at this point, a few customers of AMD buying Opteron were The Weather Channel, Siemens, Boeing, Lockheed, Ferrari, Racksaver, Volkswagon, Rackspace, University of Kentucky (these are the ones to have publicly stated they adopted Opteron whose news articles to the effect I could find). Revenue of Q3 2003 was $1.2 billion (about $2 billion today), and that was the first quarter to include AMD64.