All the Mods 10 launched on NeoForge for Minecraft 1.21, and the question everyone asks is whether it is worth moving from ATM9. The answer depends on what you value: familiar content, new mods, performance, or server stability. Here is how they compare.
The Basics
| ATM9 | ATM10 | |
|---|---|---|
| Minecraft version | 1.20.1 | 1.21.1 |
| Mod loader | Forge | NeoForge |
| Mod count | ~400 | Around 500 |
| Maturity | Fully stable | Active development |
| Java version | Java 17 | Java 21 |
ATM9 has been out long enough that most bugs are fixed, most mod interactions are documented, and the community knows the optimal progression paths. ATM10 is newer, which means more active development but also more patches, more config changes, and more surprises.
Mod Differences
What ATM10 Added
ATM10 benefits from mods that moved to NeoForge and 1.21:
- Newer Create builds with updated features and better performance
- NeoForge-exclusive mods that were never backported to Forge 1.20
- Updated world generation from Minecraft 1.21 changes
- Java 21 optimizations including Generational ZGC support
What ATM10 Lost (Temporarily or Permanently)
Not every mod has made the jump from Forge 1.20 to NeoForge 1.21:
- Some tech mods are still catching up. If your favorite niche mod is not in ATM10, it might not have updated yet.
- Certain compatibility patches between mods need time to be rewritten for NeoForge's changed API
- Recipe integrations and quest line polish are still being refined
Check the ATM10 mod list on CurseForge before committing. If a mod you consider essential is missing, stay on ATM9 until it arrives.
Core Mods in Both
The backbone of both packs is the same: Create, Applied Energistics 2, Mekanism, Thermal Series, Botania, Ars Nouveau, and the usual utility mods. If you play ATM for the core tech and magic progression, both packs deliver.
Performance
Server Performance
ATM10's server files ship an 8 GB Java heap (-Xmx8G in user_jvm_args.txt), so plan for more RAM than on ATM9, not less. On either pack, the load grows with what your players build and keep loaded, such as big automation setups, chunk loaders and several busy dimensions.
Client Performance
Client FPS depends mostly on your hardware, render distance and shader or resource pack choices. ATM10 runs on Java 21 with newer builds of its rendering mods, but frame rate on its own is no reason to switch packs. Try both on your own PC if it matters to you.
Server Requirements
ATM9
| Players | RAM | CPU | Storage |
|---|---|---|---|
| 1-2 | 8 GB | 3.5 GHz+ single thread | 15 GB |
| 3-6 | 10-12 GB | 4.0 GHz+ single thread | 20 GB |
| 7-12 | 12-16 GB | 4.0 GHz+ fast single thread | 25 GB |
ATM10
The official ATM10 8.2 server files (Minecraft 1.21.1, NeoForge 21.1.251, Java 21) ship a user_jvm_args.txt with -Xmx8G, so the pack itself asks for an 8 GB Java heap. Java needs memory on top of the heap, which is why we size ATM10 like this:
| Players | Plan RAM |
|---|---|
| 1 to 5 | 12 GB |
| 5 to 15 | 16 GB |
| 15+ | 32 GB |
Raise -Xmx in user_jvm_args.txt when you move to a bigger plan, or Java keeps using 8 GB no matter how much RAM the server has. Our All The Mods 10 server hosting page has these plans ready to order. On Space-Node Minecraft hosting, the Premium tier with a Ryzen 9 7950X or 9950X (depending on stock) is the strongest option for either pack, because kitchen-sink modpacks lean hard on single-thread speed.
Stability
ATM9
Stable. Years of patches, known issues documented, workarounds established. If you start an ATM9 server today, you will have a predictable experience. The pack receives maintenance updates but no major changes.
ATM10
Actively developing. You will get patches every few weeks, some of which may change recipes, add mods, or adjust balance. This is exciting if you like new content, but disruptive if you run a public server where players expect consistency.
For a community server with a wipe schedule (start fresh every few months), ATM10 is fine. For a long-running world that you want to be stable for a year, ATM9 is the safer choice.
JVM Optimization
ATM10 on Java 21 opens up Generational ZGC, a garbage collector built for large heaps. There is no server.jar to put flags on: a NeoForge server starts through run.sh, which reads its Java flags from user_jvm_args.txt. The shipped file holds -Xms4G and -Xmx8G. On a 12 GB plan, for example, change it to:
-Xms4G
-Xmx10G
-XX:+UseZGC
-XX:+ZGenerational
Keep -Xmx about 2 GB below your plan's RAM, because Java needs memory outside the heap as well. ZGC keeps its pauses very short even on a big heap, where G1GC can cause the occasional stutter while it collects garbage.
ATM9 on Java 17 is best served by G1GC with Aikar's flags (the traditional recommendation).
Progression and Content
Both packs use a quest book to guide progression. The general flow is similar:
- Basic survival and base building
- Early tech (Create, basic power generation)
- Mid-tier automation (AE2, Mekanism processing)
- Advanced magic (Ars Nouveau, Botania)
- End-game (creative items, dimension exploration, ATM star)
ATM10's quest book is still being refined. ATM9's quest book has been polished over multiple updates and provides a smoother guided experience. If you are new to kitchen-sink modpacks, ATM9's quest book is a better teacher.
Which One Should You Choose
Choose ATM9 if:
- You want a fully stable, mature pack
- You are running a long-term server (6+ months without resets)
- A mod you need has not updated to NeoForge 1.21
- You are new to ATM and want the most polished guided experience
- Your server is already running ATM9 and players are mid-progression
Choose ATM10 if:
- You are starting a new world
- You want the latest mod versions and features
- You want Java 21 and Generational ZGC on the server
- You do not mind occasional updates that change things
- You want to take advantage of Minecraft 1.21 world generation
The pragmatic answer for mid-2026: if you have no existing ATM world, start with ATM10. The mods are more current, it runs on Java 21, and the pack will continue receiving content updates. If you are already invested in ATM9, there is no rush to migrate. Your world and your progression are worth more than a newer mod list.
FAQ
Can I transfer an ATM9 world to ATM10? No. The packs target different Minecraft versions (1.20.1 vs 1.21) with different mod loaders (Forge vs NeoForge). World data, mod IDs, and block registries are incompatible. You need a fresh world for ATM10.
Is ATM10 harder than ATM9? The difficulty is comparable. Some recipes changed, some progression paths shifted, but the overall challenge level is similar. If you found ATM9 easy, ATM10 will feel the same.
Can I add mods to ATM10? Yes, but with caution. Adding mods to a kitchen-sink pack increases the chance of conflicts. Add one mod at a time, test, and back up your world before adding the next. Check the ATM Discord for known compatible additions.
How much RAM do I really need? For a server with 3 to 4 friends: 12 GB for ATM10, because its server files already set an 8 GB Java heap, and 10 GB for ATM9. Monitor usage after the first week. If you consistently use over 80% of your allocation, upgrade.
Which pack has more content? ATM10. Its current files have around 500 mods, against roughly 400 in ATM9. Content depth (quests, progression, integration) is comparable.
Related guides: optimize your ATM server with ZGC vs G1GC comparison and ATM10 server optimization guide. For ATM10 specific setup, see server requirements and JVM arguments. Browse all recommended mods in best Minecraft mods 2026.