Nobody knows. There’s no clear cut answer for this; some say it was intended to be every 20 frames, and there was an off-by-one error in implementation. https

Nobody knows. There’s no clear cut answer for this; some say it was intended to be every 20 frames, and there was an off-by-one error in implementation. https://ggn00b.com/for-noobs/frame-rule-mario-explained/ https://ggn00b.com/for-noobs/frame-rule-mario-explained/