E-Series Firmware downgrade with USB drive?

[juusso]

so to elaborate.. <...>
.. since one of latest official firmwares this is no more brick issue as they improved failure catching.

Would like to see if TV isn`t in bootloop (because of authuld) if no proper signx.bin is flashed, mismatch. If this is for sure removed on latest firmware (where this knowing comes from?), does it mean, no cmacs are checked at all?

[dajojo]

so to elaborate.. <...>
.. since one of latest official firmwares this is no more brick issue as they improved failure catching.

Would like to see if TV isn`t in bootloop (because of authuld) if no proper signx.bin is flashed, mismatch. If this is for sure removed on latest firmware (where this knowing comes from?), does it mean, no cmacs are checked at all?

if im correct it means if sign0 is crippled (firmware upgrade interrupted or so) then bootloader would auto switch to sign1 and second partition. maybe this is why samsung greyed out the option to revert to former firmware since they use it for dual boot now ?
i have no idea what is checked, i presume if checksums for sign0+partition0 not right it boots to sign1+partition1 which is copy of sign0+partition0 made on succesfull boot after flash and forced restart of tv. strange thing is cam software firmware get upgraded after this restart when you turn off the tv it upgrades.
got this from my tv as i crashed it a while ago trying to poke into port9090 with a zeus hack lol
somewhere along the way it lost the watchdog also but before behaviour was like i crash it and tv would hang and after few minute reboot automaticly. now it hangs and restarts tv and smarthub is screwed up and some stuff is hanging. after few restarts of tv it gets corrected and tv boots normally. before i had to factory reset. i think it was firmware 1015 after this it changed.
edit: offcourse 2nd os partition need to have all the correct keys n checksums in order otherwise its brick. i also tried installing newer firmware which had wrong dirname, tv would not see it so i changed the info file and tv didnt see it and i changed dirname and it sees it and upgrades firmware.. til 95% and then it crashed.. i restarted tv and old firmware back. furthermore the usa samsung developer site got some little hints for the firmware changes. it also speaks of changes in the firmware upgrade routine.
i was thinking .. in service menu you can upgrade firmware for microphone and camera directly, this is taken from original firmware from usb. maybe there is a way to use this, since this get triggered normally on shutdown of the tv.