m15 R1, can't undervolt?

There is a way to undervolt this computer even with the restriction Dell has put after bios 2.0 which forbids downgrading to previous versions where undervolting was possible.

I've came up with this solution as a workaround and it should do for anyone : 

Now let me preface by saying if this is the first time at all you're trying to mess up with the bios of your machine, you can skip step 1 to 4 and this will most likely work rolling you back into a Bios version that supports undervolting BUT, if you've done step 5 at least once, then there is a high chance that you will need to go over step 1 to 4, because the way the UEFI firmware is designed in this computer is that he automatically detects critical outdated BIOS version and will proceed to upgrade without your consent if you didn't disable some options in the BIOS previously before doing step 5.

TL/DR : If you haven't done step 5 ever in your life skip 1 to 4, otherwise don't.

1 - Download the most recent Bios version that supports undervolting at format .rcv, in this case 1.6.2 works perfectly.

2 - Mount the EFI partition by opening the cmd prompt as Admin and type :

mountvol X: /s

3 - Download the Explorer++ (Free, Open Source app) to manipulate the files on the EFI partition :

4 - Open explorer ++, then browse the EFI partition like so : EFI > Dell > Bios > Recovery

(Keep in mind all of the following operations under 4- must be made in explorer ++, it will not work in classic windows explorer because it will refuse to display the EFI partition)

In EFI > Dell > Bios > Recovery you will find three files one for the current bios tagged "BIOS_CUR.rcv" one for the previous version "BIOS_PRE.rcv" and there is a third "BIOS_BIR.rcv" but I don't know for which operation that last one stands.

When I did my first attempt I couldn't make sure which file for sure was going to work although there was a high chance that PRE_BIOS alone would be enough to override.

So what i did was :

- Create a backup of all three files under /Documents

- Copy three times, the bios .rcv file downloaded in step 1., and name each version as "BIOS_PRE.rcv", "BIOS_BIR.rcv" and "BIOS_CUR.rcv"

- Copy and paste those 3 renamed files into /EFI/Dell/Bios/Recovery overriding the original files (that we've already backed up just in case)

Now the hard part is done you're almost there.

5 - Shutdown the computer and disconnect the AC

- Press and hold esc + ctrl

- reconnect the AC while holding esc + ctrl

- wait for .5 sec then release

This will initiate the Bios Recovery mode and will then prompt you with 3 options, at that point you will chose to ROLLBACK  which will then load one of the three files we've overrided previously (it's probably the BIOS_PRE file, lurring the system into thinking he's loading a legit version.

This way you're guaranteed to downgrade anytime you want to any version you want.