FPS Drops In Nether

Unstable Frame Per Second in nether.

What I expected to happen was...:
FPS in nether being somewhat playable.

What actually happened was...:
FPS is very unstable and can range from 0 to the average on my PC which is 150. It constantly drops to 0 and freezes. Even during pre-loaded areas. In the overworld, I get about 100+ FPS constantly.

Steps to Reproduce:
1. Go into the nether.
2. Check FPS while moving around.
3. Result.