Hi Gerry,
I always had a pretty good run out of the parallel port and had a very good 'flat line' DriverTest.exe response. As such I did not expect to see
a dramatic improvement when I went to a SmoothStepper.
What I got impressed me, I had been running my 5 phase Vexta steppers at 1800 rpm during G0's without good reliability under the parallel port.
When I switched to the ESS I was able to increase the G0 speed to 2400 rpm and run marginally cooler. Also the sound the motors make it not as harsh.
I ascribed, maybe mistakenly, that the 2-4us of jitter of the parallel port was sufficient to induce a rather harsher noise than the same motor under the ESS.
The only time I got into any bother with the parallel port is if I had some CPU intensive task running in the background or a large file where the redraws would
either stop, stall or stutter Mach. I've found the ESS to be somewhat more forgiving in that regard.
The increased range of highly suitable PC's and OS's that come from using a good external motion controller lead me to recommend such a controller alone.
The perceived, real or otherwise, increase in performance is a bonus.
Craig