[x280] Undervolting permanantly disabled? BIOS downgrade blocked!

[Bookoflife]

Trying to extend battery life + lower temperatures by undervolting X280. This thread shows good results from doing so + other threads for T480 say the same thing.

According to this comment, BIOS must be downgraded to pre-plundervolt mitigations.

Plundervolt came in Nov/Dec 2019 (source) so looking at x280 bios update txt log the version required is 1.30. All versions available here from Lenovo.

Despite successfully downgrading to 1.33, I cannot get 1.30 to install either with mkusbkey.bat or from within Windows.

Finally, attempts to downgrade using winflash64 directly with the /sd (skip date) command does not work - "secureflash authentication failed" error.
Maybe a different version of winflash? Some versions have /sv command to skip version check, see here.

- Should I just use the /force command with winflash?
- Do I need a SOIC8 + RPi to downgrade to 1.30 and earlier?
- Does anyone have any advice or recommendations? All thoughts/opinions very welcome.

[RealBlackStuff]

Maybe replace the BIOS chip with another one, that has the version you need?