I'm doing some motion tracking, and to quickly edit things I preload the frames into the memory. However, this fills up my ram, and sometimes (e.g when I'm not working with the footage) I want to clear it out of memory. Can this be done?
It should be done automatically. Old stuff won't be hold as you can see when you lower your used RAM amount in the System settings to a few MB. Only the last few frames would be hold in your RAM. Watch it in the Movie Clip Editor as you play your footage.