Steps to change the DVMT value (Done on Windows or WinPE)
/!\ Warning, some files in attachment will show as infected, you'll need to disable your antivirus temporarily
Use at your own risk!
1) Universal BIOS Backup ToolKit 2.0.exe - to backup the BIOS (i.e. DellInc.-A07.rom)
2) UEFITool.exe to find the module labeled SetupPrep (not Setup as per FireWolf’s guide) and extract the PE32 image section (setup.bin)
Update:
For Dell Only: Search with this GUID, right click the GUID found and select extract body. Save it as setup.bin
899407d7-99fe-43d8-9a21-79ec328cac21
3) Universal IFR Extractor.exe to extract setup.bin to a readable text file
4) Use notepad to search for “DVMT” in the text file
i.e. for the E7450, 2 were found at 0x432 and 0x433 but only 0x432 needs to be changed to 0x3
5) Format an USB drive to fat32 and create a folder name EFI
6) Download the EFI Shell and extract the Boot folder to EFI folder (EFI/Boot/bootx64.efi)
7) Boot system with the USB and select UEFI Boot
At the grub prompt, enter these commands, hit enter after command, then exit and reboot
i.e. setup_var 0x432 0x3
To verify if the value was updated, just enter setup_var 0x432 and hit enter, the value will be listed
More detailed instruction in attachment
/!\ Alternatively, just use Lilu.kext + Whatevergreen without having to mess with the BIOS
https://github.com/vit9696/Lilu/releases
https://github.com/vit9696/Lilu/blob/master/KnownPlugins.md
https://github.com/acidanthera/WhateverGreen/releases
DVMT_Tools.zip