Atmosphere version 1.2.1 releases, supports Switch firmware 13.1.0

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Less than a day after Switch firmware 13.1.0 went live, popular custom firmware Atmosphère has already been updated to support it. The Hekate bootloader also received an update around the same time, so you may want to update that while you're updating Atmosphère. You can find links to these projects' GitHub pages below, as well as the official patch notes for Atmosphère 1.2.1.

:download: Atmosphere Download Page
:arrow: Atmosphere Discussion Thread
:download: Hekate Download Page

1.2.1 is Atmosphère's fifty-eighth official release.

Please be sure to update fusee when upgrading to 1.2.1. fusee-primary no longer exists, and will not work any more.

With thanks to the @switchbrew team, Atmosphère 1.2.1 is bundled with hbl 2.4.1, and hbmenu 3.4.1.

The following was changed since the last release:

  • Support was implemented for 13.1.0.
    • mesosphère was updated to reflect the kernel behavioral changes made in 13.1.0.
      • KScheduler now issues a data memory barrier when unlocking the scheduler lock and when early-returning due to top-thread-is-current during scheduling.
    • erpt was updated to reflect the latest official behaviors.
      • The new service added in 13.0.0 ("sprofile") was revised, and the data formats it expects was changed.
        • This still appears to be (possibly(?)) untestable due to data not being transmitted yet, but I have greater confidence things will go smoothly than I did when 1.1.0 released.
  • A number of improvements were made to mesosphère, including:
    • A build target was created to build targeting the qemu virt board.
      • This facilitates writing unit tests for the kernel (and other atmosphere components) and running them under PC.
        • Please Note: Official system software will not work at all under this, and the Atmosphère project has zero interest in attempting to run official software of any kind. This is unit testing machinery, and explicitly not more than that.
      • This should hopefully allow us to have greater confidence that all of atmosphere's components work the way they're theoretically supposed to in the future.
      • Please Note: If you are a developer who is familiar with the Horizon operating system (or capable of becoming familiar), I would greatly appreciate help writing tests and improving the testing framework.
        • Please contact SciresM#0524 if you are capable and interested.
          • Really, if you are actually a developer who would like to help me get this off the ground, I would deeply appreciate it.
          • That said, if you are not a developer but want to be one, this probably isn't the best opportunity; I expect it to be highly technical.
            • Consider the ReSwitched discord's #hack-n-all channel for your educational purposes.
        • We are (at least for now) using catch2 for unit tests.
    • Almost all virtual calls in the kernel are now resolved statically.
      • This eliminates substantial virtual call overhead, and should lead to improved kernel microperformance in pretty much every function.
    • The remaining red black tree find operations which weren't using the optimized "find key" variant are now using the optimized version.
    • Custom assembly was written to improve tick-to-timespan conversion.
      • This works around gcc emitting suboptimal assembly at -Os (it emits good assembly at -O3, clang is fine at both -O3 and -Os).
    • KThread and KSession structures were updated to optimize member layout, saving 0x10 bytes per KThread/KSession object.
    • Rather than unnecessarily zero-ing all data in kernel objects only to overwrite members later, we now only initialize the members we need to in kernel object constructors.
      • This is what Nintendo was doing already.
    • A set of custom optimized atomic primitives were implemented and are used in place of std::atomic<>
      • This works around a gcc bug which downgrades specified memory order to seq_cst, and introduces clrex in places where it is appropriate.
      • This should strictly improve microperformance of many system calls.
    • An compile-time toggleable extension was added to support 40-bit physical addresses in MapRange capabilities (using currently reserved bits).
    • A number of minor bugs were fixed, including:
      • Initial cache management now better reflects official behavior.
        • This fixes an issue that caused certain hardware with cache sensitivity to produce cryptic kernel panics during boot.
      • Incorrect logic when checking thread priority capabilities was fixed to reflect official behavior.
      • The scheduler was updated to reflect latest official behavior, and a number of minor bugs involving clz/ctz were fixed.
      • Accesses to the processes local region were fixed to properly use kernel linear region, not userland pointers.
      • The cache SVCs exposed for 32-bit processes now better reflect official core mask request semantics.
      • A bug was fixed that could cause a kernel panic if SvcArbitrateLock was called on a thread with exactly one reference in the middle of handling a user-mode exception.
  • General system stability improvements to enhance the user's experience.
For information on the featureset supported by 1.2, please see the official release notes.


Button Masher
May 19, 2008
Is it possible to play N64 games on a hacked console that doesn’t go online, or is being online a requirement?


New Member
Oct 26, 2021
I also dumped my 13.1.0 with tegraexplorer and tried to upgrade my emunand with Daybreak, but after checking that the update was valid (so I am sure it has been dumped correctly) it complained about "exfat validation failed" error code something and a missing package with a content id. It prompted me to continue but I decided not to. Did you get the same warnings and proceeded regardlessly or was it just me?
Well, I did not get this warning. But do you know if your stock firmware supports Exfat? If not, you have to install this support when is updating the Emunand. I followed one guide, but I cannot link here, because I am a forum newbie user. So I'll post the part of the text citing the emunand update:

Updating your emuMMC with Daybreak​

  1. In Hekate go to Launch -> Atmosphere FSS0 Emu.
  2. Once booted, hold R while launching a game to boot into the homebrew menu.
  3. Find Daybreak in the homebrew menu and launch it.
  4. Tap on Install and navigate to tegraexplorer/Firmware/<latest firmware number>.
  5. Tap on Continue and then Preserve settings.
    • If you see the message Warning: exFAT firmware is missing or corrupt, you likely don't have the exFAT drivers installed on your sysMMC. Just press continue if this is the case.
  6. If it is available choose Install (FAT32 + exFAT), otherwise Install (FAT32) and then Continue.
  7. Wait until Daybreak completes installing the dumped firmware.
  8. Once it completes, it will ask if you want to reboot. Tap Reboot.
  9. Once rebooted, launch into emuMMC and verify your system works. You can verify your system has been properly updated in Settings -> System.
Credit: nh-server github io

In item 5 you can see the quote about the exfat notice
Last edited by danbroken,
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Well-Known Member
Jan 3, 2016
Been using atmosphere for a while now. I see somewhere that the new atmosphere and fusee.bin are no longer compatible with the sx dongle that i use to boot atmosphere. Is there any truth in this?
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