I am currently using a ESS on a x86 machine. Although Mach 3 is capable of running on an x64 windows system, just not using the parallel port. When using MACH 3 on a x64 bit system a controller of some sort needs to be used.. A ESS, a uc100, uc400, etc..
If you use an x86 windows machine (desktop) you can most likely add in a cheap parallel addon card.. ($10). If you are using a laptop to run MACH3 and any variation of windows (x86 / x64) you will most likely need a external controller. A ESS, a uc100, uc400, etc.., unless you are fortunate enough to have a parallel port on the laptop..