Yes it is.I have a 1995 4020HT with CNC88HS control in format 1.... Is my control too slow to handle the circular/linear interpolations any faster?
Couple things to try that may give slight improvement.
1) Run your DNC at the highest baud rate (38400 I think). If you are running 9600 your DNC is starving the control.
2) Turn off acceleration (G8). If you have hard corners this may hammer.
3) The very best thing to do (especially with " a simple flat surface w/ a 3/8" radius transition") is to change the toolpath from linear segments into circular interpolation (1 line of code instead of 1000). I do not know the capabilities of your CAM, but this is always my priority with my programs and doable within my CAM. It also has the benefit of often making the program small enough to be run from the control. It is amazing how arc fitting can change 80,000 lines into 12,000.
The control will not show actual feed only programmed feed.