Minecraft Frames Per Second Drop from 1.5.2 to 1.6.1/1.6.2

When I first open a world (single/multiplayer) in 1.5.2. The Fps is around 60fps(max). So it is playable with no lag. Now when I update to 1.6.1/1.6.2. The Fps drop tremendously. going around 7-28 fps on max. I tried using a different launcher (Magic Launcher) and changing the settings. But none of this works. So now it is unplayable with now exception. This problem will effect a lot of players playing on there laptop(no gpu). I suggest changing the requirements of Minecraft or fixing this bug. This is the worst bug i seen in the official version of Minecraft.