What computers do I need

[JAZZCNC]

100% backup what i2i says and will add that Mach3 main program works fine with 64bit it's the Parallel port driver that doesn't and CAN NOT be used on 64bit PC's and why folks use Smooth stepper or some other motion control device.

Any memory stick works fine with Mach3 but what you should do to be safe, esp with very long G-code files is copy them onto the hard drive before loading into Mach3. When you load a G-code file into Mach it buffers the code and if very long pulls from the loading device and Memory sticks can be picky and sometimes not fast enough to respond which can cause Mach problems.!

The biggest problem most folks have with Mach comes from the PC's parallel port and not the actual PC or it's Spec. In fact often the newer and more powerful the PC the higher chances are you'll have issue's.? This comes from the fact most modern PC's have low power 3V parallel ports fitted.

So like i2i suggests P4 machines or PC's of that era often work great.
If like my self and Mad Prof you use a external motion controller like the smooth stepper then lots of issues are eliminated with some nice fringe bennifits. The best being you can use any PC equipped with either USB or ethernet from really low spec laptops to all singing all dancing 64bit rocket ships and get much much smoother and often faster performance than you can from the PP.!!