I made buffer logging and yes, buffer level hits to bottom pretty easily on arc moves. Even without LCD or SD. When it is human noticeable (stuttering) the situation is very bad. Some help can obtain by tweaking parameters but 8-bit Atmel is just too slow for delta calculations (when there are lot of arc moves). Increasing buffer I can get rid of the worst stuttering but in log I can see underruns.
Axel.
Axel.