I've also done a bunch of machine control, and I generally really like the multi CPU architecture for real time control, if you are making your own hardware, I

I've also done a bunch of machine control, and I generally really like the multi CPU architecture for real time control, if you are making your own hardware, I don't think it is too extreme. I've also found a lot of the systems end up being a mix of hard/soft realtime, where the bits that directly monitor/control the machine are hard, and then there is soft "decision" type stuff, farming them out to their own CPUs is often much easier to make guarantees of the hard real time bits.