New PC - motherboard parallel port differences

[Neale]

OK.. so if I go the planetCNC ethernet controller route.. what shall I do about the PC situation?

The problem with PC and PP is that every so often, the cpu goes off and does its own thing for a few milliseconds or so. That's fatal if you are generating a real-time pulse stream. However, if you are using an external motion controller, the PC sends a few seconds' worth of instructions which are then buffered in the external board. It doesn't matter if the PC pauses for a short while as it can catch up later while the motion controller is taking data from its own buffer. Cheap PC or even laptop (notorious for random pauses) should be fine. Buy or build PC - it's up to you.