So i recently built my new PC (ill post Spece down below) and i can run minecraft well over 200 fps but only in fullscreen or a little window, Not in a full windowed mode. when i maximize the window in minecraft my fps goes from about 300 straight to 60-70. i know that my pc isnt the problem because i can run it perfect in full screen or a tiny window so whats the problem here? I am running 64 bit java too and have optifine installed, please help!!
Specs:
Gtx 750 Ti 2GB SC
Intel i5-4590
8GB Ram
1TB HDD