Real time operating systems

I have been reading all the EMC for Unix stuff with great interest. But
I really don't want to go through the pain of converting my home CNC
over to Unix. My experience with Unix is that it is a catch 22 of
sorts: it is a really cool operating system because it is an open
standard; it is also a real pain in the ass because its an open
standard. But I have been thinking about something ever since I read
that the decision to go Unix was for real time determinism. Wouldn't it
be fairly simple to create a FIFO memory buffer between the computer and
motor controller such that it buffers motion commands from a
non-realtime computer and issues them in real time? The FIFO would not
even need to be very deep if you had a feedback to the computer to tell
it "I'm full now, stop transmitting". I don't know the EMC program
structure, so I don't know how hard this would be to implement in code.
But it seems simple, and would open the door to using any operating
system.

Mike