Installing Windows in UEFI Mode

Motivation – Booting Windows in UEFI mode offers a couple mild advantages:
  1. it’s more compatible with Clover if you’re booting OS X this way already
  2. it’s supposedly the fastest boot sequence
For motherboard: Gigabyte GA-X99-UD4

Notes / Lessons Learned:

  • Disconnect all other drives than the one installing to
    1. existing windows drives get targeted for reusing their boot partition and wouldn’t create all 4 “ideal” GPT UEFI partitions present on a cleanly installed drive (Recovery, System, MSR, Primary)
    2. having my Mac Clover drive connected during these attempts allowed the setup utility to clobber my Clover boot with the Windows bootloader …
      • reinstalling Clover via VMware OS X guest DID NOT put the UEFI Clover bootloader back in charge!
      • had to delete/rename efiwindows folder and only then did the old EFI option start showing back up on the "BBS” bios boot volume picklist (F12)
  • Rufus flash usb boot tool – for my mobo, wound up working best with mbr and uefi-csm (counter to prevalent recommendation)
  • what really seemed to matter was putting the usb stick in a certain USB port! i used the chassis USB header with 2x USB3 and 2x USB2… going from left to right it was the second USB3 port that worked; the left port most never did
  • BIOS settings
    • fast boot didn’t seem to matter either on or off
    • legacy usb worked in disabled mode
    • worked with “other OS” selected
    • disabled CSM never worked – machine would not display bios after reboot (contrary to most UEFI guides' recommendation)

To Confirm:

from “WinPE” environment:
  • Shift F10 to open command window
  • wpeutil UpdateBootInfo
  • reg query HKLMSystemCurrentControlSetControl /v PEFirmwareType
  • Looking for 0x2 = UEFI (0x1 = legacy)
from real Windows:
  • msinfo32.exe > System Summary > “BIOS Mode” – looking for “UEFI” (“Legacy” means not UEFI)

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