Specialties between BIOS and UEFI Windows flash installation media?

  administrator, service, windows

What I noticed about problem:

"Install.wim file provided in the Windows 10 1809 ISO download from Microsoft is over 4 GB in size.
We need to have our boot USB formatted as FAT32 in order to boot properly on some first generation UEFI computers, and FAT32 has a file size limit of 4GB."

UEFI iso images must contain:

  • ‘el torito emulation specifier’ (‘Etfsboot.com’)
  • ‘platform id’ from implemented UEFI specification by manufacturer of motherboard device
  • ‘binary floppy disk layout’ (‘Efisys.bin’)

Some USB disks formatting tools are using some fixes appending them to the end of flash drive partition, while they write iso image to the flash drive.

Source: Windows Questions