Minecraft and Terraria both run incredibly slow on my machine. I've never seen anything like it, javaw.exe hammers my cpu - it's constantly at 100%. These aren't even graphically intensive games, they both use java, so I suspect that to be the reason.

I tried setting low render distance, 3D anaglyph to off, graphics to fast, but still minecraft became unplayable.

I uninstalled all previous versions of java and installed the latest version: jre7. I even tried running minecraft in very low resolution and it still killed by cpu. Reinstalling minecraft and java hasn't worked.

I've checked that nothing else is running, anti-virus autoscan is off.

I've managed to run hl2, portal, cod4, san andreas and other recent 3D games just fine, so it's very frustrating.

My specs: Pentium 4 2.8GHz 1 GB RAM NVIDIA 5600 64MB Windows XP

  • 1
    I was going to say this belonged on Superuser, but their FAQ rules out games... I don't know the solution, but I'll note that I have Windows XP/SP3 (DirectX 9c), Pentium 4 E8400 CPU, 2GB RAM, and an NVidia 7600, and Minecraft runs fine. Could be your memory or graphics card - try updating your graphics card drivers before getting a new card, though. :)
    – Cyclops
    Commented Jul 16, 2011 at 17:30
  • 7
    Except, as far as I know, Terraria was written in C# on top of .NET and XNA...
    – Bobby
    Commented Jul 16, 2011 at 18:10
  • Are you sure it's the games, and not a third-party process/application?
    – Bobby
    Commented Jul 16, 2011 at 20:56
  • 1
    javaw is using 100% of the CPU, or the CPU is at 100% and javaw is one of the running processes? Commented Jul 16, 2011 at 21:44
  • Do you by any chance have a virus scanner running? If they're set to paranoid, they can be a real resource hog. I've got an AMD X2 4200 with 2G (6 years old :), and a ATI 4300 and both Minecraft and Terraria run acceptably. That said, close all other applications (browser and so on), as Minecraft wants that 1G of RAM all for itself!
    – yatima2975
    Commented Jul 16, 2011 at 23:19

1 Answer 1


You could try and tune javaw. To begin with i assume you run it like this :

C:\jdk6\bin\javaw.exe -jar "C:\jedit\jedit.jar"

To add parameters for tuning, it should then look like this :

C:\jdk6\bin\javaw.exe -Xmx256m -Xms256m -jar "C:\jedit\jedit.jar"

The above example allocates 256 MB heap memory for Java.

Further examples can be found in the Java Tuning White Paper.

Good luck :)

  • How exactly is this related to javaw consuming 100% CPU time?
    – Bobby
    Commented Jul 18, 2011 at 15:58
  • If javaw runs out of memory it will become very slow or errors might even appear. Using the above tip you can tweak the memoryusage, so the games can run better. Note that 1GB of ram is very little, according to this page (buxville.net/showthread.php/…) Minecraft will take up 500MB for itself. You should consider adding more memory to your system.
    – Sharken
    Commented Jul 18, 2011 at 17:55
  • I didn't know that it was related this way.
    – Bobby
    Commented Jul 18, 2011 at 18:21
  • If java starts maxxing out memory, it'll spend more and more time doing garbage collection and your cpu usage will get out of hand.
    – spudone
    Commented Jun 30, 2014 at 23:39

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