-Xmx2G -Xms2G -Xmn768m -XX:+DisableExplicitGC -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+UseNUMA -XX:+CMSParallelRemarkEnabled -XX:MaxTenuringThreshold=15 -XX:MaxGCPauseMillis=30 -XX:GCPauseIntervalMillis=150 -XX:+UseAdaptiveGCBoundary -XX:-UseGCOverheadLimit -XX:+UseBiasedLocking -XX:SurvivorRatio=8 -XX:TargetSurvivorRatio=90 -XX:MaxTenuringThreshold=15 -Dfml.ignorePatchDiscrepancies=true -Dfml.ignoreInvalidMinecraftCertificates=true -XX:+UseFastAccessorMethods -XX:+UseCompressedOops -XX:+OptimizeStringConcat -XX:+AggressiveOpts -XX:ReservedCodeCacheSize=1024m -XX:+UseCodeCacheFlushing -XX:ParallelGCThreads=10


adjust -Xmx and Xms as necessary leaving 1GB or more for your system, and -XX:ReservedCodeCacheSize should be half the allocated RAM.

Install optifine and put all settings to max and watch your FPS skyrocket! Enjoy! :D I run ~1GHz CPU so this really helped me get ~60-80+ FPS at times.