if you have a recent intel chips, they all speak amd64 (aka x86_64) etc. you can install 64bit kernels on any of these machines. basically, if you have a core series processor or above (with literally like 3 exceptions), you processor speaks the predominant 64-bit instruction set. so this is just a software not a hardware issue. naturally, if you're running an AMD chip, they have been speaking amd64 since the K8 core. (> 10 years)