Hacking Restoring Nand backup with a burnt fuse

[falby]

I have an unpatched Erista on Firmware 11.0. Was running SX OS without using emuNAND.

I installed Atmosphere recently and it works well. Still no emuNAND. Still Firmware 11.0.

I want to setup emuNAND and upgrade to latest firmware with Atmosphere.

I have a NAND backup on Firmware 4.1.0 and a NAND backup on Firmware 5.1.0. I burnt a fuse updating to 5.1.0. After that all my updates where with Choi, AutoRCM enabled so no more fuses burnt, and I haven't connected to Nintendo's servers since updating to 5.1.0.

NAND backup of 4.1.0 should be clean but 5.1.0 will be dirty with some XCIs having been run but I might get away it.

I have previously successfully restored my 5.1.0 backup when I wanted a clean start and that worked fine.

Will it be possible to restore 4.1.0 even with the burnt fuse?

 

[Hayato213]

You can try, it is 1 fuse count difference between 4.1.0 and 5.1.0. Make a backup of Current NAND before restoring.

 

[kidkat210]

Burnt efuses mean nothing unless you plan on booting your sysnand without going through a bootloader/directly into cfw.

Also you only burn efuses when you boot into sysnand without going through a bootloader/directly into cfw

For example, you boot into hekate to boot into stock ofw (no cfw), it skips the efuse check and burning of said efuses. But if you were to have autorcm disabled, turned off your switch and turned it back on without pushing any payloads, booting to ofw. THEN you would burn efuses and go through the efuse check

 

[falby]

Burnt efuses mean nothing unless you plan on booting your sysnand without going through a bootloader/directly into cfw.

Also you only burn efuses when you boot into sysnand without going through a bootloader/directly into cfw

For example, you boot into hekate to boot into stock ofw (no cfw), it skips the efuse check and burning of said efuses. But if you were to have autorcm disabled, turned off your switch and turned it back on without pushing any payloads, booting to ofw. THEN you would burn efuses and go through the efuse check

So therefore it's viable to restore my 4.10 firmware so long as I boot OFW via Hekate after the restoration? And I could then update sysNAND to the latest firmware using OFW? The objective is to get back to my cleanest sysNAND before setting up emuNAND.

If I didn't have AutoRCM enabled when I made my 4.1.0 NAND backup, will I still have AutoRCM after restoring? Or would I have to be really careful to boot to hekate and not OFW after restoring using a jig etc.

 

[Draxzelex]

So therefore it's viable to restore my 4.10 firmware so long as I boot OFW via Hekate after the restoration? And I could then update sysNAND to the latest firmware using OFW? The objective is to get back to my cleanest sysNAND before setting up emuNAND.

If I didn't have AutoRCM enabled when I made my 4.1.0 NAND backup, will I still have AutoRCM after restoring? Or would I have to be really careful to boot to hekate and not OFW after restoring using a jig etc.

Custom bootloaders like Hekate bypass the fuse check which is whole reason we can update without burning fuses; the same principle applies to booting firmware versions lower than the fuse count.

As for AutoRCM, it returns the console into the state it was in when the backup was made. Imagine turning back time on your console. Either way, you can always check if AutoRCM is enabled or disabled after the restoration and proceed from there.