Whenever I launch Minecraft.exe on my computer, while the Minecraft launcher is loading, my computer starts to lag out. The render rate on my entire computer slows down . This is participially noticeable with moving the mouse pointer or while watching videos while it is starting.

After the launcher has loaded, everything goes back to normal. I log in and I can play the game fine.

I have tried uninstalling all Java installs and reinstalling only the latest Java 64bit with no luck

My computer, operating system install and Java install are all 64bit.

My system specs are as follows:

Operating System
        MS Windows 7 Home Premium 64-bit SP1
        AMD Phenom II X4 840    38 °C
        Propus 45nm Technology
        8.00 GB Dual-Channel DDR3 @ 666MHz (9-9-9-24)
        SyncMaster (1440x900@60Hz)
        1023MB GeForce GTX 550 Ti (ASUStek Computer Inc)        39 °C

My Java installs are as follows:

List of all my Java installs

  • Your computer specs would help (a lot) with this question.
    – Dracs
    Commented Aug 26, 2012 at 11:48
  • I have added those to the question.
    – njallam
    Commented Aug 26, 2012 at 11:58
  • Which version of Java you have installed is probably very relevant too. Could you add that? If you have multiple versions installed, it would be helpful to include all version info, as Minecraft has a habit not using the Java version you think it should. Commented Aug 26, 2012 at 15:12
  • 1
    Yes, that's helpful! It sounds like your using Java 7? I've heard reports that it doesn't run Minecraft well. If you downgrade to Java 6, does it still lag? Commented Aug 26, 2012 at 19:28
  • 2
    It is always A+ ok to post useful, relevant information.
    – kotekzot
    Commented Aug 27, 2012 at 6:40

1 Answer 1


Thanks to @SevenSidedDie, I discovered that the error only occurrs when running it with JRE7. This was tested by uninstalling JRE7 and instead using JRE6.

However, as a Java developer, it was really inconvenient to have the the latest Java runtime uninstalled as I need it to debug with. I reinstalled JRE7 and after some tinkering, I did the following to force it to run with JRE6:

Forcing Minecraft to run with JRE6

  1. Make sure you have both JRE6 and JRE7 installed.
  2. Move Minecraft.exe somewhere out of the way, otherwise it will run with the JRE7 (hence causing the problem). I use the "%AppData%.minecraft" folder.
  3. Make a shortcut to Minecraft.exe in your Start menu - You can do this by dragging with your right-mouse button into the All Programs section of the Start menu. Get rid of the "-Shortcut" bit if you wish by right clicking on it and clicking Rename.
  4. Right click on your shortcut and click Properties.
  5. Under "Target:" enter (with the quotes)"C:\Program Files\Java\jre6\bin\javaw.exe" -jar "%AppData%\.minecraft\Minecraft.exe"
  6. Make sure that "Start in:" is set to %AppData%\.minecraft
  7. Click Apply and/or OK.

Now, whenever you want to run Minecraft, start it from the Start menu. This also works if you pin the Start menu icon to the taskbar.

  • As an alternative to that you could use Magic Launcher instead. It replaces the Minecraft.exe launcher, while providing more functionality (including selecting Java executable). minecraftforum.net/topic/…
    – Dracs
    Commented Aug 27, 2012 at 8:03
  • Nice! Glad I could nudge your investigation in a useful direction, and thanks for the detailed instructions on how to work around the problem when someone wants to have both installed. (Remember to come back and mark this answer as accepted after the waiting period is done.) Commented Aug 27, 2012 at 17:20

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