While playing Minecraft, CPU usage skyrockets

[Newfie]

Tried this from a Live USB with Fglrx (persistance).

When playing Minecraft, I noticed major lag spikes. Upon checking top, I found that Minecraft consistently uses at least 130% in CPU resources. I have a 6 core PC, so this is pretty crazy.

Does this without fail every time the game is launched.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: openjdk-7-jre 7~u3-2.1-1ubuntu3
ProcVersionSignature: Ubuntu 3.2.0-22.35-generic 3.2.14
Uname: Linux 3.2.0-22-generic x86_64
NonfreeKernelModules: fglrx
ApportVersion: 2.0-0ubuntu4
Architecture: amd64
CasperVersion: 1.314
Date: Mon Apr 9 16:22:25 2012
LiveMediaBuild: Ubuntu 12.04 LTS "Precise Pangolin" - Beta amd64 (20120408)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: openjdk-7
UpgradeStatus: No upgrade log present (probably fresh install)