My only experience outside Linuxcnc is the big dollar industrial controls from many years ago so I won't try to compare to everything else available.
My machines are all open loop and the motherboards are old Atoms that really should be replaced except for laziness and the 'don't mess with a running piece' mindset.
Step pulses are software.
That situation has happened. Whether due to something running in the background or the low spec of the hardware, the computer could no longer responded to mouse and keyboard, what people sometimes call freeze or lock-up. The machine didn't lose a beat and the part was good.
I first learned what exists inside/outside realtime the hard way. With a large program loaded keyboard jogging did something unexpected due to response lag.
Now finally to the question.
Does using external hardware (Mesa or other) reduce that response lag ? Question asked in relation to possibly adding an MPG to one machine.
btw: 109 That last sentence ? We know what you meant.