Re: [CAD_CAM_EDM_DRO] What is EMC ? part II

Tim wrote:

> >From my understanding it was originally written for NT with a commercial
> ($$$) real time kernel. If I remember this is still on the NIST site
> somewhere.

No, it originally ran on Sun (Unix) workstations, as a software exercise.
They ran a K&T mill at GM powertrain and some other machines with a
Delta-Tau motion board, with plain NT. The experiment with the RT
option to NT was a failure, as the interrupt latency was all over the map!
It ran from 100 uS to 1.4 seconds, if I recall! Clearly unacceptable for
a machine tool motion servo loop. I suspect there must have been
something wrong, or they chose a very SOFT real time package vendor,
rather than a hard real time one by mistake.

After the awful performance tests with the NT real time package, they tried
the early RT-Linux, and were very impressed by the average interrupt
latency (about 20 uS on a 100 MHz Pentium, I think) as well as the WORST
case latency was no worse than 100 uS. This was clearly something you
could live with for 1 KHz or so servo cycle times.

Jon