Try lowering the settings, it should help. You can also try to allocate the game some more ram (you can easily find some tutorials for that). These things helped me to raise the performance of my computer. Now it runs smoothly, and I have no lags at all. Everything is ok even when I run those beautiful and heavy worlds created using the seeds from ethershock. You should definitely try these 2 methods, it should help. I am sure that it's going to work