How to Allocate More RAM for the modpacks

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When I input -Xmx4G or 8G doesn't seem to do much, I still get around 14-25 fps in windowed and at most 40fps in fullscreen. If someone could help me out with the java arguments that would be great! I have 16GB of RAM and 64bit java offline.


New Member
Jul 29, 2019
If your FPS is low its NOT because of insufficient memory allocation. Insufficient java memory would manifest as periodic deadlocks as the Java VM tried to scavenge more memory, followed by crashes, when Minecraft tries to access things it tried to load but couldn't.

Low FPS is caused by a crappy video card or video drivers.


Popular Member
Aug 24, 2013
Define Crappy XD i don't really get it... most lappys or desktops use for gamig should be able to handle the stress of MC.

sent from a phone using tapatalk.
Said many a MC player complaining that their high end gaming rig chuggs like mad when playing modded....

Take a look at your processor. Video cards are great for games when the game is made to actually use one, unlike MC where you have to tell your card to work for java (not MC). Using your video card will take some of the stress off of your CPU and may help performance. Also, I'm not sure if this is the case anymore, but MC only uses 1 core of your CPU... So a quad core is not helping.. :)


New Member
Jul 29, 2019
You don't have to tell your video card to work for Java.

Ok, you do: In a very specific scenario: IF you have a Laptop with dual graphics cards - a low power one and a "performance" one, THEN and ONLY THEN does this advice apply: The Graphics drivers try to save power by running non games on the low power card and they usually detect games by checking the name of the exe file. Because minecraft runs under Java.exe, more typically associated with "enterprise" software, its detected by default as not a game and routed to the low power GPU.

For laptops with intel graphics chipsets / drivers, this is probably the purpose of the very strange "MojangTricksIntelDriversForPerformance" parameter passed to Java if you've ever looked in the crashlog.

At any rate, if you have a laptop with "hybrid performance graphics" then the display control panel will hopefully contain a section where you can register exe files - such as java.exe - to be detected as games.

Back to @AngelloHalo - the memory allocated to Java is not going to be behind these performance issues. If you can look in the Game Output log in your launcher there should be a bit about "System Details" that looks like this:

-- System Details --
    Minecraft Version: 1.7.10
    Operating System: Windows 10 (amd64) version 10.0
    Java Version: 1.8.0_25, Oracle Corporation
    Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
    Memory: 108372064 bytes (103 MB) / 255066112 bytes (243 MB) up to 3207856128 bytes (3059 MB)
    JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx3G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
    AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
    IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
    GL info: ' Vendor: 'NVIDIA Corporation' Version: '4.5.0 NVIDIA 353.82' Renderer: 'GeForce GTX 650/PCIe/SSE2'
If you can find that we can see what your MC instance actually has available to use.