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SkyFactory 4 & FTB StoneBlock: FPS & Crash Fix Guide

1 minGuide
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Memory tuning (4 GB – 6 GB), Java 8 or Java 17 setup, and crash troubleshooting for SkyFactory 4 & FTB StoneBlock in Prism Launcher.

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Target Modpack
SkyFactory 4 & FTB StoneBlock
Required Java
Java 8 or Java 17
Optimal Heap RAM
4 GB – 6 GB
Loader
Forge (1.12.2 / 1.16.5 / 1.20.1)

Eliminating lag spikes and stutters in SkyFactory 4 & FTB StoneBlock

When running SkyFactory 4 & FTB StoneBlock on Windows, stutter usually comes from either too little heap memory or an over-allocated heap (>12 GB) causing long JVM garbage-collection pauses.

Lock your instance memory inside the **4 GB – 6 GB** sweet spot and verify that `javaw.exe` is assigned to your dedicated NVIDIA or AMD GPU in Windows Graphics Settings.

Prism Launcher screenshot showing the modpack installation user-interface
Modpacks install as their own instance, so they stay clean and easy to update.

Fixing startup crashes and updating safely

  1. Confirm your instance uses **Java 8 or Java 17** under Edit Instance → Settings → Java.
  2. Before updating the modpack to a new release, right-click the tile and select Copy Instance so your existing world and configs have a rollback point.
  3. If a crash persists, click **Upload** in the Minecraft Log tab to generate an mclo.gs diagnostic link. Get the latest Prism build at /download.

Frequently asked questions

Why does SkyFactory 4 & FTB StoneBlock crash before reaching the title screen?

90% of pre-title-screen crashes on SkyFactory 4 & FTB StoneBlock happen because Prism is pointing at the wrong Java major version instead of Java 8 or Java 17.

Can I add extra performance mods or shaders to this pack?

Yes. Open Edit Instance → Mods → Download mods to add FerriteCore, ModernFix, or Iris/Oculus matching your loader.

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Prism Launcher on Windows showing several modpacks and instances