Just want to clear this one up. KSP, etc was only using 2.8GB of memory previously likely due to the fact that while running in the 32bit address space, no application (or Operating system for that matter) can address more than ~3.7GB of memory. 2.8GB sounds around about right. KSP (and the Unity engine for that matter), as a responsible application will make memory management choices that allow the rest of your system to keep running smoothly. You are using a lot of mods, some of which would benefit greatly from the ability to address a much larger amount of memory. KSP again has made an informed decision to expand into a much larger memory space due to the requirements of everything that is running within it. Spend some time with all your mods on in the x64 version and you may find, though it is still Early Access so you may not, that it is a much smoother experience. If you disregard the current known issues. As for me, I am experiencing most of the known issues so far. They are pretty frustrating at times. Though overall the experience has been quite positive. Chris