I've read a warning in a DELL Guide (here) about editing the DVMT Pre-allocation using the EFI Shell
Warning for 4k / UHD screen owners:
Do not use the EFI shell to to edit the DVMT Pre-allocation for getting your screen to work. This bricked a user's machine already. Instead, make use of a patch explained in a lower section of this guide
Yes. Messing around with settings not provided by the BIOS carries a certain amount of risk...
I have no idea on the applicability of the advice in that thread for your hardware, since your profile is not filled out with details...
Please provide complete details in your profile/signature
(Profile/Settings link in upper right corner of this site)
Mobo: manufacturer/model + bootloader(Clover/Chameleon/Chimera)
CPU: detailed CPU model + motherboard chipset
Graphics: all graphics devices + laptop internal screen resolution
For example, typical Ivy laptop:
Mobo: HP ProBook 4540s (Clover)
Graphics: HD4000, 1366x768
Use CPU-Z on Windows to find CPU (Core iX-xxx) and motherboard chipset (HMxx), and graphics capabilities. For a laptop, these details are important and affect critical installation procedures.
Note: When specifying your bootloader, if using Clover legacy, please be sure to specify "Clover legacy"). Specifying "Clover" will be assumed as "Clover UEFI"