2020-04-27 18:40:22 +01:00
# fusée
fusée is a custom bootloader used to start the Atmosphère environment.
It is divided into three sub-components: fusée-primary, fusée-mtc and fusée-secondary.
2020-04-26 19:06:59 +01:00
2020-04-27 18:40:22 +01:00
fusée is also capable of chainloading other payloads (e.g.: Android).
2020-04-26 19:06:59 +01:00
2020-05-03 15:49:23 +01:00
fusée's behavior can be configured via the [BCT.ini ](../features/configurations.md ) file located on the SD card.
2020-04-26 19:06:59 +01:00
2020-04-27 18:40:22 +01:00
## fusée-primary
fusée-primary is the first piece of Atmosphère's code that runs on the hardware.
2020-04-26 19:06:59 +01:00
It is distributed as a standalone payload designed to be launched via RCM by abusing the CVE-2018-6242 vulnerability.
2020-04-27 18:40:22 +01:00
This payload is responsible for all the low-level hardware initialization required by the Nintendo Switch, plus the extra task of initializing the SD card and reading the next fusée sub-components from it.
2020-04-26 19:06:59 +01:00
2020-04-27 18:40:22 +01:00
## fusée-mtc
fusée-mtc is an optional, but heavily recommended sub-component that performs DRAM memory training.
This ensures a proper environment for running the final fusée sub-component.
2020-04-26 19:06:59 +01:00
2020-04-27 18:40:22 +01:00
## fusée-secondary
fusée-secondary is the last fusée sub-component that runs on the system.
2020-04-26 19:06:59 +01:00
It is responsible for configuring and bootstrapping the Atmosphère environment by mimicking the Horizon OS's design.
2020-04-27 18:40:22 +01:00
This includes setting up the cryptosystem, mounting or emulating the eMMC, injecting or patching system modules and launching the exosphère component.
