I hear that cpu just fetches instruction from the `EIP` register,never fetches from memory directly.

But AFAIK,`EIP` just stores the **address** of the next instruction,the instruction itself is still in the memory.If CPU never fetches memory,how can it know what the next instruction actually is?

**UPDATE**

BTW,I know there're x86,x64,x87 architectures,but which does `x86-64` belong to,`x86` or `x64`??