Modern/compact linuxcnc setup

Guys, thanks for the advice.

bbsr_5a: budget is not unlimited but I'm also not worried about spending 100 bucks more for a better setup (it only has to save a couple of good end mills over it's lifetime to pay itself back

BeagleBrainz: thanks for the details. If I go with Mesa (either Ethernet or SPI) I'm I right to assume that I won't have to worry too much about base thread latency and I could probably be ok with a preempt-rt setup? If I don't have to worry too much about getting rtai to be happy I'm less concerned about going with a pi setup (not sure how well arm support is).

I'm pretty convinced Mesa is the way to go, mostly because it's hard to find small mother boards with parallel ports.
Between Ethernet and Pi SPI, what would be the best interface?

In all honesty I'd run with a std PC setup with Ethernet. Latency, with in reason, is not such an issue with the Nesa Ethernet boards.
An RPi4 would probably work with ethernet as well as it's on the PCIe bus now and not on the USB bus.
An RPi with Spi works to all accounts, but, and this is not a slur on the Mesa gear, I think Ethernet will still be with PC's for a while and is an option for the RPi. Where as with the RPi and SPi you are kind of locked into one platform.
Given a little extra cash I wouldn't mind playing with and RPi 7c80 or 7c81 setup.

I've got a Atomic Pi sitting on a shelf that although I've installed Linuxcnc uspace on with an RT kernel I haven't had a chance to test with my setup.

Makes a lot of sense.
If I stick to a standard itx, any particular advantage to a Mesa via pcie (maybe I could use a riser and manage to fit the Mesa in a super compact itx case).

Other question: in case I wanted to upgrade to linear encoders with Mesa, do I have to worry about the interface? I don't know enough about the internals to understand if the encoder feedback is going to be handled by the fpga or if there is going to be a round-trip to the linuxcnc thread.

Honestly if the MB goes belly up Ethernet just needs a cable unplugged from the old and plugged into the new, no PCI or PCIe card to worry about.
I have a second LAN card in my 1u rack case, connected via riser, but I only put that in for hooking up to my local LAN.

I'm not up on encoders and such so maybe one of the gurus will chime in.

Not a guru but one typically would use the 7i85s daughter board. Or all-in-one with the 7i95.
Look for the 25-pin fpga expansion connector. I use 7i76e+7i85s combo but many variants will work like 7i96+7i85s.

Ethernet gives flexibility, I tried the 7i76e on the Rpi4 with good result.
I think one can have somewhat faster servo-thread (2-3 kHz?) with pcie, but never felt a need to go faster than the default 1 kHz.

maghis wrote: I've looked around and unfortunately there are not many mobos that come with a parallel port today.

If you want one, check out the mini-itx.com "board finder"
www.mini-itx.com/store/category?type=mot...&sortby=price&page=1
Right at the bottom on the left you can choose parport or parport header (if you choose both there will be no results)