Allow Minecraft to Use More CPU

Solution 1:

(Unmodded) Minecraft isn't multithreaded, so splitting it across multiple CPUs is not possible. However, I am not sure about a mod to allow for this possibility. There might be other factors you are ruling out.

From what I have found the mod, OptiFine, is supposed to split the load across two cores. (Otherwise, Minecraft only uses one)

OptiFine 1.2.4 Mod adds a lot of options for better looks and performance. Doubling the FPS is common. Moves fog away, adds mipmaps, chunk loading control (mod CAF), Smooth FPS, brightness control, VSync and many other.

Screenshot of Optifine below:

Solution 2:

I installed ThrottleStop and gave Minecraft a higher FID (in my case, 10 instead of 6).

Now Minecraft uses the full 2.5GHz of my processor instead of capping at 800MHz or so. It runs smooth as butter.

A word of warning, however: if you're using a laptops, you do want to keep an eye on the heat situation before the computer shuts off on you.

Solution 3:

The fix for my performance issues was using the 64 bit version of the Java runtime. After that was installed Minecraft ran much better.

64-bit Java can be downloaded here: http://www.java.com/en/download/manual.jsp

To my understanding, the 64-bit Java runtime only gives Minecraft access to more RAM. Yet this fixed the performance issue.