Cray owes its survival to AMD. The company was bought by SGI in 1996, hollowed out, and spun off in 2000 with very little left. SGI had taken most of the talent and IP.
Desperate for a win, Cray began working with Sandia National Labs in 2002 to build a supercomputer based on x86 technology. Intel at the time was dismissive of 64-bit x86 and was promoting Itanium. AMD had other plans and was in the process of developing Athlon for desktops and Opteron for servers.
The project came to be known as Red Storm, starting with single-core Opterons and upgrading to dual- and quad-core CPUs as they hit the market. Red Storm ranked as high as number two on the Top 500 list of supercomputers. More important, it served as the basis for the XT3 line of supercomputers that revived Cray as a player in that field, and lit a fire under Intel as well.