I MAY be speaking out of turn because I have not looked at the manual for a while. I know with my 305 and 301(I think the number) I had to clear memory going into a race to assure the unit did not lock up when the history register filled. I am of the thought that the 610 does not need to be cleared; rather, it overwrites the oldest data in the register. That prevents the dreaded lock up mid run. Again, I may be mistaken but I do not remember ever dumping history on the 610