English Switch's eFuses. What are they?

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Switch's eFuses. What are they?​

When we talk about updating the console to a new version, there is a lot of talk about eFuses, but do you know what they are?

It is a microscopic physical fuse that is in the processor, and since it is physical, once burned it can no longer return to its original state.

What is it used within the Switch?

Our console uses eFuses to tell what version we are on and to prevent you from being able to downgrade to a previous version.

How does the Switch check the burnt eFuses?

As soon as it boots (in the bootloader) it checks the version we have installed and the eFuses we have burned.
Burnt eFuses always have to be one more with the firmware version we are on. For example, if we are on version 6.0.0 the eFuses burned must be 7.

If for example Nintendo releases an update from 6.0.0 to 6.1.0, no eFuse will be burned as revisions don't count, so we will still have 6 eFuses burned, eFuses will only be burned when we go from one version (for example from 5.0.0 to 6.0.0).

You must bear in mind that if you have 7 eFuses burned (because you are on version 6.0.0) and you want to downgrade to version 5.1.0 using ChoiDujourNX, you will not be able to, since as soon as you start the console it will detect that you have 7 eFuses burned and at being on version 5.1.0 the console will stop immediately.

This verification is done only through the official bootloader if, for example, we try to do the same but we boot the console with the CFW SX OS, the system will let us boot since it does not check the eFuses, but the sleep mode will not work for you so that when you turn off the screen you will not be able to turn it on again without having to restart.

Here is a table with the firmware version and the burned eFuses:

System version: It is the version of the operating system in which you are
Expected number of burnt fuses (retail): These are the burned eFuses that you should have if you have updated through settings (if you have updated through ChoiDujourNX you should not have uploaded the eFuses).

Can you update console firmware without burning eFuses?

Of course! We have made a guide so you can install a new firmware version without burning eFuses. And all thanks to homebrew ChoiDujourNX!

Watch the guide for installing new firmware with ChoiDujourNX

If you have any questions, post a message and we will help you! Do not be shy!