Both machines are older Teknic SST Servos. The ones stepping are SST-1500-ACX, and only accept step/dir inputs. The machine originally was setup software stepping using an old DOS PC running Microsystems of Buckannon software (Company eventually became WinCNC.) I eventually converted it to Linuxcnc still software stepping. I was never happy with the servo tune or performance (with either system) and eventually added a Mesa 5i25/7i85S combo to add hardware stepping and encoder feedback, to try to improve the servo tuning. It did make tuning easier but the performance improvement was never seen mostly due to issues of compliance in the drivetrain and general bad design/poor engineering of the machine (what it really needs is about double the gear reduction and stiffer drive train.)
The other machine has Teknic SST-3000-UCX drives Because of the tuning issues I was having at the time with the step/dir servos on the other machine (this was before I added the hardware stepping and encoder feedback) I really wanted to try an analog system. Unfortunately I ordered the wrong drive version and the UCX version only did step/dir or analog torque commands. (I should have ordered the VCX version.) The online documentation I was looking at lead me to believe that the UCX one could have also done velocity commands but I was wrong. The drives came in TCX, RCX, UCX, VCX, and YCX versions and their descriptions seemed very ambiguous and incomplete to me. I've digressed.
My main point here is if there was any problem with delays inherent to Linuxcnc or the Mesa analog 5i25/7i77 system I'm using, my torque command machine set up would not be usable at all. (A torque command system is much more response time sensitive than a velocity commanded one.)
