[toast0]

Firmware v1 requires a switch with zero fuses blown.

Firmware v2 requires a switch with no more than one fuse blown and blows the first fuse.

If you install v2, you can't install v1.

Nintendo can make 22 firmware releases that disallow rollback.

[jtbayly]

Got it. Thanks. For some reason I was imagining a new firmware that some people couldn’t install because they had blown too many fuses.

[toast0]

Yeah, that shouldn't happen (although I think I've seen reports of eFuses blowing spontaneously as well as eFuses self-repairing)

If your console blows a fuse before Nintendo intends to, you won't be able to install firmware until a firmware is released that will run with that number of fuses blown. And, depending on how things are implemented, you might not be able to run the firmware that you have either.