RCM (short for ReCovery Mode) is a mode for the switch that allows nintendo to send the switch commands to do various things. People found out that on unpatched switches, you could send a payload, and then quickly copy it into the memory buffer behind the stack, overflowing the memory buffer into the stack, meaning you smash the stack and get full access to everything on the system. We use it here to launch atmosphere.
emuNAND vs emuMMC vs sysNAND
- sysNAND stands for System NAND, meaning the internal storage in your actual Switch.
- emuNAND stands for emulated NAND, this means that your entire NAND (system memory) will run off your microSD card with Custom Firmware (CFW). This NAND's contents (games, applications, saves, etc.) are completely separate from your sysNAND.
- emuMMC is the name for the currently used implementation of emuNAND on Switch. It has no difference from emuNAND besides name.
emuNAND CFW (Recommended)
What's needed for emuNAND
- A microSD card that's 128GB or larger
Pros of using emuNAND over sysNAND CFW:
- Installing game cartridge dumps or doing homebrew without "dirtying" sysNAND, allowing sysNAND to be used online without ban risk.
- Allowing users on patched Switches using Caffeine to update their emuNAND to latest and use it online, keeping sysNAND at a lower vulnerable version.
Cons of using emuNAND over sysNAND CFW:
- games saves between sysNAND and emuNAND will not be same and you need to sync saves somehow and it is risky process. (disable emuMMC in hekate and boot CFW over the sysnand and inject the game saves via EdiZon)
sysNAND CFW (Not Recommended)
This is for the people who don't have an 128GB microSD card or larger, or who don't want emuNAND for whatever reason.
This method would be best for people who only do pkhex or any saves editing and wants same game saves on sysnand.
If you set up an emuNAND you may still have CFW on your sysNAND if you choose to use it. You do not have to follow the guide linked below; all the files are the same, you simply select "sysNAND CFW" from Hekate/Nyx.