Hello,
I recently started playing ATM9 and I encounter a problem launching the game, entering the world manager , and launching my world...
It just freeze and, if I dare to click, it crashes
The RAM shouldnt be the problem as I tried with 20GB allocated and still got the issue
So if anybody could help me I would be grateful

Just a heads up, the loading speed goes back to normal if I create a new profile instead of trying to upgrade/downgrade. If it matters, it gets stuck on the "COMMON_SETUP" step

Having the same problem. It was working fine on 1,0,5, even tho it was taking a little bit its justifiable considering the quantity of mods. However 1.0.6 sends the cpu usage to like, 2% and gets stuck eternally loading. Something changed that made the game load slower

The modpack actually suggested (in-game when you have less than you should) 12Gb based on specs. If 12GB is not the suggested that should be updated.

Whats your ram speed btw if you head into your task manager and under performance you can see your memory speed there

It's DDR 5, and I know it's 5000+ but not on that PC ATM to check.

nah too easy.... yeh def try lowering it and give that a shot.... maybe the suggested doesnt take into account what your pc also needs to use to run smoother.... I dunno weird

assigning too much ram @Warc0 can also make your game load slower. Make sure all your drivers are up to date and also make sure your ram is installed in the correct slots in your pc. Also see if you can overclock your ram... that helped me in loading it way faster. I only have assigned 9GB of ram out of my 32gb... whats your pc specs if you dont mind me asking i may be able to help you performance manage your pc to help load minecraft faster

@CollinHerber Try allocating 8GB of ram and see if it loads quicker. If it does allocate more and more to see where it starts to slow down your pc
my cut off is 9gb
otherwise if i allocate more i tend to get issues

I was also experiencing this

• GTX 4090
• 7900x
• 64 GB (12GB Allocated)

If I just simply let it launch - Don't touch it and wait the ~4-5 minutes it will eventually work. If I click or lose focus it's game over.

Whats your ram speed btw if you head into your task manager and under performance you can see your memory speed there

try restarting the pc only if it gets stuck on "COMMON_SETUP" step

Just a heads up, the loading speed goes back to normal if I create a new profile instead of trying to upgrade/downgrade. If it matters, it gets stuck on the "COMMON_SETUP" step

re-installed the pack and it works perfectly fine...for now at least
btw I allocated around 8GB RAM I get around 300fps without shaders

Also stuck in the COMMON_SETUP step. According to the logs (if I force-quit) it is very busy doing textures.

Strange thing though is that it worked just fine the past few days, just right now it suddenly decided to stop working, and it reliably no longer starts. RAM slowly ticking upwards, but even after 20 minutes (normally startup time for me is ~2 minutes) I am still at this step.

[22:50:00] [Worker-ResourceReload-11/INFO]: Dispatching ForgeZModel$ModifyBakingResult (as ZModel$ModifyBakingResult) to 1 listener
[22:50:36] [Render thread/INFO]: Mixing client.MixinRowHelper from mixins/common/nochatreports.mixins.json into net.minecraft.client.gui.layouts.GridLayout$RowHelper
[22:50:36] [Render thread/INFO]: Mixing client.MixinChatOptionsScreen from mixins/common/nochatreports.mixins.json into net.minecraft.client.gui.screens.ChatOptionsScreen
[22:50:36] [Render thread/INFO]: Renaming synthetic method lambda$init$0(Lnet/minecraft/client/gui/components/AbstractWidget;)V to mde13cc2$lambda$init$0$0 in mixins/common/nochatreports.mixins.json:client.MixinChatOptionsScreen
[22:58:00] [Render thread/INFO]: Stopping!
[22:58:00] [Render thread/ERROR]: Shutdown failure!
java.util.ConcurrentModificationException: null
	at java.util.HashMap.forEach(HashMap.java:1432) ~[?:?]
	at net.minecraft.client.renderer.texture.TextureManager.close(TextureManager.java:178) ~[client-1.20.1-20230612.114412-srg.jar%23994!/:?]
	at net.minecraft.client.Minecraft.close(Minecraft.java:1070) ~[client-1.20.1-20230612.114412-srg.jar%23994!/:?]
	at net.minecraft.client.Minecraft.m_91393_(Minecraft.java:1043) ~[client-1.20.1-20230612.114412-srg.jar%23994!/:?]
	at net.minecraft.client.main.Main.main(Main.java:234) ~[forge-47.2.20.jar:?]
	at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103) ~[?:?]
	at java.lang.reflect.Method.invoke(Method.java:580) ~[?:?]
	at net.minecraftforge.fml.loading.targets.CommonLaunchHandler.runTarget(CommonLaunchHandler.java:111) ~[fmlloader-1.20.1-47.2.20.jar:?]
	at net.minecraftforge.fml.loading.targets.CommonLaunchHandler.clientService(CommonLaunchHandler.java:99) ~[fmlloader-1.20.1-47.2.20.jar:?]
	at net.minecraftforge.fml.loading.targets.CommonClientLaunchHandler.lambda$makeService$0(CommonClientLaunchHandler.java:25) ~[fmlloader-1.20.1-47.2.20.jar:?]
	at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:30) ~[modlauncher-10.0.9.jar:?]
	at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:53) ~[modlauncher-10.0.9.jar:?]
	at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:71) ~[modlauncher-10.0.9.jar:?]
	at cpw.mods.modlauncher.Launcher.run(Launcher.java:108) ~[modlauncher-10.0.9.jar:?]
	at cpw.mods.modlauncher.Launcher.main(Launcher.java:78) ~[modlauncher-10.0.9.jar:?]
	at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:26) ~[modlauncher-10.0.9.jar:?]
	at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:23) ~[modlauncher-10.0.9.jar:?]
	at cpw.mods.bootstraplauncher.BootstrapLauncher.main(BootstrapLauncher.java:141) ~[bootstraplauncher-1.1.2.jar:?]

(Please note the gap of 8 minutes at which point I force-quit the application.)

Possible solution
After deleting the directory local in the mod dir the game launched properly again. This is where most FTB mods do their local caching, so it should be safe to delete.