Indeed. Although both processors follow the x86 architecture (list of instruction sets, which in theory makes them compatible for applications in almost every way), when it comes to graphics the companies have different patented technologies.
AMD uses 3DNow!, SSE, SSE2, etc.
Intel uses MMX, (some of the newer ones I don't remember)
And these instruction sets govern how the CPU deals with certain multimedia aspects of a system. While they are built on the same basic set of rules (just like x86), they will still handle specific operations differently.
Nor would I be surprised if Intel has influenced the software development of Everquest to work against 3DNow! for their latest version