Eliminating lag spikes and stutters in Fabulously Optimized
When running Fabulously Optimized 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 **2 GB – 4 GB** sweet spot and verify that `javaw.exe` is assigned to your dedicated NVIDIA or AMD GPU in Windows Graphics Settings.
Modpacks install as their own instance, so they stay clean and easy to update.
Fixing startup crashes and updating safely
Confirm your instance uses **Java 21 (for 1.20.5+)** under Edit Instance → Settings → Java.
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.
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 Fabulously Optimized crash before reaching the title screen?
90% of pre-title-screen crashes on Fabulously Optimized happen because Prism is pointing at the wrong Java major version instead of Java 21 (for 1.20.5+).
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.
