Lenovo Thinkpad 8 tablet: possible BIOS lockdown?

My Lenovo Thinkpad 8 tablet is equipped with an Intel Z3770 cpu and runs Win 10 32-bit. I would like to install 64-bit Win10 which comes with a useful Linux bash shell. My BIOS appears to be locked down to 32-bit UEFI and can’t boot the 64-bit installer from a USB drive. In the Console OS Wiki I found this info:

I am running BIOS v1.71 and wonder whether it could be true what the Console OS guys are writing that some BIOS configuration switch prevents me to boot 64-bit EFI and if so can it be unlocked ?

I started reversing the installed BIOS and found out there are a couple of NVARs, like “BIOS Read/Write Protection, Variable: 0x321” and “TXE HMRFPO, Variable: 0x231” and “TXE Firmware Update, Variable: 0x232”. I tried to set these EFI NVARs with grub, but that didn’t work , for example setup_var 0x232 or setup_var2 0x232 both return nothing. When I boot Ubuntu 15.04 from a USB stick I can access /sys/firmware/efi/efivars and see a lot of files, e.g. System-e947fcf9-dd01-4965-b808-32a7b6815657

Now for my question, how can I find the efivars file which corresponds with for example “TXE Firmware Update, Variable: 0x232” ?

I did find the Setup-ec87d643-eba4-4bb5-a1e5-3f3e36b20da9 NVAR in the bios dump and I patched following variables which are included the Setup NVAR:
TXE, Variable: 0x22F -> 0x00 disabled
TXE HMRFPO, Variable: 0x231 -> 0x01 enabled
TXE Firmware Update, Variable: 0x232 -> 0x01 enabled

Unfortunately, still getting error 26 locked by flash descriptor

Does any of you have an idea what can be done? I have attached the IFR file ("File_DXE_driver_CFEF94C4_4167_466A_8893_8779459DFA86_PlatformHiiAdvancedDxe IFR.txt") and the binary NVAR ("Setup-ec87d643-eba4-4bb5-a1e5-3f3e36b20da9.mod")

Thanks for any suggestion!

File_DXE_driver_CFEF94C4_4167_466A_8893_8779459DFA86_PlatformHiiAdvancedDxe IFR.txt (173 KB)

Setup-ec87d643-eba4-4bb5-a1e5-3f3e36b20da9.rar (250 Bytes)