ATM10 at a glance
| Minecraft version | 1.21.1 |
|---|---|
| Mod loader | NeoForge (not Forge) |
| Java | Java 21 is mandatory - the pack does not start with Java 17 |
| Scope | kitchen-sink pack with several hundred mods, continuation of the ATM series |
| Source | CurseForge - installable with a click in the panel |
| Goal | ATM Star, extended with the content of Minecraft 1.21 |
| Special feature | considerably higher RAM requirement than ATM9 |
| Recommended plan | plan XL - plan L only for very small groups |
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ATM10 server hosting
Prepaid from €2.99 / month, unlimited slots, no minimum term. The right plan is listed in the RAM table below.
Plans & pricesThe switch to NeoForge and Java 21
ATM10 is not a simple update of ATM9, but a break in two places. First, it runs on NeoForge instead of Forge. NeoForge emerged from Forge and works identically for players, but it is a loader of its own - mods for Forge 1.20.1 cannot simply be carried over.
Second, Minecraft has required Java 21 since 1.20.5. If you start ATM10 with Java 17, the server aborts immediately and writes an UnsupportedClassVersionError referring to class file version 65 to the log. That is by far the most common error with this pack and fixed in two minutes: in the web interface under Startup, set the Docker image to Java 21 and restart the server. The mapping of Minecraft to Java versions is covered in detail in Change the Java version.
An existing ATM9 save cannot be transferred to ATM10. The world formats of 1.20.1 and 1.21.1 differ, and so do the mods' item registries. ATM10 is always a new run.
Why ATM10 needs more memory
ATM10 uses noticeably more than its predecessor. That has less to do with the number of mods than with the foundation: Minecraft 1.21 keeps more data per chunk, and the freshly ported mods are not yet as optimized as their 1.20.1 versions, which matured over years.
As a rule of thumb, ATM10 has come to need around 2 GB more than ATM9 at every stage for an otherwise identical group. In practice, this means: what ran on ATM9 with 8 GB needs more like 16 GB on ATM10. For a group with several players who want to automate seriously, plan XL is the realistic starting point. Plan L works for two to three players in the early phase, but hits its limit as soon as larger machine chains and several dimensions come into play.
Conversely: if money is tight or you are continuing an older run, you are no worse off with ATM9 - it remains the more resource-friendly of the two releases.
With us, memory is taken proportionally from the plan via -XX:MaxRAMPercentage. So you do not have to maintain an -Xmx value in the start command - a plan change takes effect immediately without you changing anything in the start command.
When ATM10 is the right choice
ATM10 pays off if you want to take the content of Minecraft 1.21 along and are starting a fresh run. The mod landscape on 1.21.1 now has the most important names together, and if you start from zero, you lose nothing.
A concrete plan with add-on mods speaks against ATM10: if you want to extend the pack with additional mods, the choice for 1.20.1 is still larger. In that case, ATM9 is the more pragmatic basis. If you want to try several packs of the same family, you will find further curated alternatives at a similar level under FTB modpacks.
Which plan for ATM10?
The thresholds below apply to this pack - a light Vanilla+ pack and a kitchen-sink pack with a hundred running machines behave completely differently. You can upgrade at any time without losing data and only pay the difference.
| Group | Plan | RAM | Price | Why | Order |
|---|---|---|---|---|---|
| 2-3 players, start | Plan L | 8 GB | €11.99 / month | Works in the early phase, but is maxed out sooner than with ATM9. | Order L |
| 4-8 players | Plan XL | 16 GB | €21.99 / month | The normal case for ATM10 - 16 GB cope with several dimensions and running factories. | Order XL |
| Late game | Plan XL | 16 GB | €21.99 / month | Multiblocks, ME networks and dimension travel run permanently. | Order XL |
| Solo, just to try | Plan L | 8 GB | €11.99 / month | For a single person, the 8 GB tier is enough to try it out. | Order L |
The memory is taken proportionally from the plan via -XX:MaxRAMPercentage - you don't need to maintain a fixed -Xmx. The basics are covered in the RAM guide.
Setting up ATM10 on the server
- Stop the server in the web interface.
- In the guided setup, choose NeoForge - not Forge. ATM10 runs exclusively on NeoForge.
- Select ATM10 via the CurseForge installer in the panel; the matching NeoForge version is set automatically.
- Under Startup, set the Docker image to Java 21. Without this step, the server does not start.
- Start the server and wait in the console until
Doneappears. The first start takes several minutes for a pack of this size. - Create a backup before the first building phase and add a daily restart in the scheduler.
Common pitfalls with ATM10
UnsupportedClassVersionError at startup
Cause: The server is still running on Java 17. Minecraft 1.21.1 requires Java 21 - the log then says "class file version 65.0".
Fix: Under Startup, switch the Docker image to Java 21, stop the server and start it again. Step by step in Change the Java version.
A mod cannot be added
Cause: The mod only exists as a Forge version for 1.20.1. NeoForge does not load Forge mods of that version.
Fix: Check on CurseForge or Modrinth whether there is a NeoForge release for 1.21.1. If not, ATM9 is the more suitable basis for this plan.
Server starts, becomes sluggish after hours
Cause: The allocated memory is too tight; the garbage collector runs constantly and slows down every tick.
Fix: Switch to plan XL - that works without data loss, and you only pay the difference. Also schedule a daily restart.
An ATM9 world cannot be loaded
Cause: World format and mod registries differ fundamentally between 1.20.1 and 1.21.1.
Fix: A transfer is not intended. Either continue the old run on ATM9 or start afresh with ATM10.