[rodw]

Latency is more of a problem with open loop steppers than it is with a closed loop system. Any hiccup in the step pulses can be thought of as an acceleration or deceleration of the stepper. A big enough hiccup and it acts like an instantaneous acceleration that the motor can keep up with and it stalls. Depending on the closed loop system you have, it can make up for the above. A closed loop cannot.

Thats not really applicable for LinuxCNC. Latency in a LCNC context is a function of the hardware. Sometimes you can fix it with BIOS settings but if its not good enough, you need to change your PC.

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.

Some Mesa cards (like my 7i76e which has 2 of them) have MPG inputs built in. I've found they work well. Mesa also make a daughter card specifically for consoles and pendants (the 7i73) so it would be possible to build a hardware pendant or console that would give full control of your machine without needing to touch the keyboard. In my case, I use a 433 Mhz wireless pendant that has a relay box/receiver inside the control box that is hardwired to the pendant buttons because when you have 32 inputs and 16 outputs you can do things like that!