Are you talking about Constant Surface Feet Per Minute or something else??
CSFM= is used on a Lathe. G96 call, G97 cancel (Fanuc/Yasnac).
Some Mills have this feature but I've never seen it used with the exception of Mazatrol Conversational Controls.
There is a feature in some CAD/CAM Softwares that decrease the Feed Rate around Corners, but other than that, it's a little confusing on this end.