55FPS? You're losing FPS because you're building. I'm on almost the SAME exact machine as you (but with 32GB RAM) and I get 7FPS on my 135MB 34 supercomputer per/minute save. The more conveyors you have the more lag you'll have. Be happy you're sitting in 40s, you'll be 30s and mid 20s soon enough. The game just isn't optimized to properly utilize all of the available hardware resources on our machines, that's all. If you're not running the newest Experimental branch patch, I suggest you do, as many people have reported anywhere from 25-65% performance gain after patch.