I downloaded Minecraft yesterday to see what the fuss is about, brilliant game!

When playing in Windowed mode, if I try and do anything else, i.e. use the computer, when the game is paused, the computer is incredibly slow, it takes a minute just to type a short message into empathy. Also, once I quit the game, the computer remains slow for about 5 minutes, until it magically frees up and becomes fast again. Could this be related to the 512mb RAM limitation of Java, and the machine is swapping?

Even trying to submit this post is incredibly slow and frustrating, it's taking me a minute just to click in the 'Tag's box.

Any ideas?

  • Ubuntu 10.10 x64
  • Intel Q9550
  • 4GB RAM
  • nVidia 8800GTS 320mb (w/prop drivers installed)
  • 1
    Can anyone verify if this happens on 32-bit Ubuntu? Dec 16, 2010 at 3:45
  • 1
    What is the output of java -version?
    – ændrük
    Dec 20, 2010 at 22:38

2 Answers 2


I had a similar issue and found my limiting the java amount of memory to the java process process, it was much faster, min 512mb, max 1gb.

java -Xmx1024M -Xms512M -cp Minecraft.jar net.minecraft.LauncherFrame

Are you using the proprietary Java RE from Sun, or the open-source version in the main repos?

Either way, I'd suggest trying the other one. I have better results with the JRE from Sun.

My laptop:

  • Ubuntu 10.4.1 (or 10.10, it slips my mind at the moment)
  • ATI x1300 Mobility with the FOSS driver
  • Intel 2GHz Core Duo (32 bit)

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