Imho GC3 has a serious memory leak.
Usually when I play, I have no issues at all, but sometimes i keep the game running over night.
And thats where the nightmares start to happen. It uses up pretty much all of my RAM when I come back to it.
Moving the view around the map leads to serious stuttering, somtimes freezes. The AutoSave can pretty much kill all processes I have running, one time it did shutdown Youtube running on chrome, it usually always stops the actual video running there.
I regularly get the Windows7 warning that I should close all programs because RAM is so low.
Yes, I have an AMD and yes, I have "only" 8 GB of RAM.
This only happens after playing for several hours OR keeping GC3 open for several hours.
Completely closing the game and loading the save fixes it, but... meh.