FPS issues while running my server

[Ankon]

Hey all, I've been having a weird fps issue when my server is running, and I want to see if I can find out what's up.

When I join the server. My fps starts at about 24-30, then slowly decreases until it's around 10-12 fps. However, when i'm looking at the ground (which happens a lot, because, you know, mining) my fps drops to 4-6 fps, and it occasionally happens when I'm looking in the direction of my machines (No fusion reactors or particle accelerators for now, just a coal generator and an enrichment chamber, simple stuff, so nothing too processor killing I would think).

However, if I look directly upwards, my framerate jumps to 80 or more, without any exceptions. Currently I'm running my graphics at fast, with smooth lighting off, particles decreased, Normal render distance and balanced performance, but this same issue also happens on high visual settings.

My computer is a Macbook Pro running a Windows 7 64 bit boot, with a 2.9 gHz i7 processor, 8 gb ram and integrated Intel HD graphics 4000 video card.

I'm currently running the server and voltz in the windows boot, because the setup is somewhat easier. The server itself has 3gb allocated, and the client originally had 3gb allocated as well, which has been reduced to 1.5gb, since the 3gb didn't seem to contribute to performance in any way.

Has anyone else had this issue? If so, did you find a fix for it? Any responses would be appreciated, since playing Voltz at 4 fps kind of sucks.