I do use while do main loop with timegettime to prduce the intervals. The problem is that on real slow comps, it doesnt skip frames, it just slows down the drawing process because it isn't fast enough to draw at the right speed.

Should it be skipping frames when it cannot maintain steady flow? Better yet...upload a small example? An example of say a ball going back and forwards using your method. That way I can see if ui am doing it differently but I don't think I am.