Cray is synonymous with "Supercomputer", in both myth and history, so it's interesting to see that in 2006, Cray will be sticking with AMD. Their next generation of supercomputers will be based upon the AMD Opteron, with servers in the years past being based also in AMD cpus, in part.

"After an extensive review of marketplace alternatives, we selected the AMD64 platform as the microarchitecture for our next-generation supercomputer products," said Cray President and CEO Peter Ungaro. "In the near-term, the AMD Opteron processor roadmap provides our customers a smooth upgrade path to multi-core systems. Through 2010, AMD's multi-core processor roadmap and HyperTransport(TM) technology capabilities stand out for their ability to help meet our aggressive performance goals."
They obviously know what they want. Cray and AMD are also working together on a U.S. government project called "High Productivity Computing Systems" for the Defense Department. Primarily the project focuses on high-performance computing that is very scalable, important since no single CPU alone could handle the tasks these large research companies require.