Legacy Boot is Greyed Out in BIOS Setup

Documentation

Troubleshooting

000032529

10/08/2021

There are several reasons why the Legacy Boot setting in the BIOS might be grayed out and can't be enabled. You may need to check each option below before you can enable Legacy Boot. 

First, be sure to check if your Intel® NUC model supports Legacy Mode as per article (000057401) - Intel® NUC Products Phasing Out Legacy BIOS Support.

Why are you seeing it? How to fix it

Modern Standby is enabled in BIOS.

Legacy Boot isn't allowed when Modern Standby is enabled.

Change the Sleep Type Support to Legacy S3 Standby:

  1. Press F2 to enter BIOS during boot.
  2. Go to the Secondary Power Settings menu:
    • Advanced > Power (in Visual BIOS1)
    • Power > Secondary Power Settings (in Aptio V BIOS1)
  3. Set Sleep Type Support to Legacy S3 Standby.
  4. Press F10 to save the changes and restart.

At the next restart after changing this setting, you'll see this message

WARNING! A change has been detected in the BIOS Sleep Type support setting, from <last sleep type> to <new sleep type>. Dynamically changing the Sleep Type support setting between Legacy S3 Standby and Modern Standby is not supported and may require reinstalling the Operating System. Would you like to continue? Enter (y) for Yes to continue, or (N) for No for reboot.

According to Microsoft, switching the power model isn't supported in Windows without a complete Windows reinstall. Changing this BIOS setting doesn't change the Windows power model.

Secure boot is enabled in BIOS.

Legacy Boot isn't allowed when Secure Boot is enabled.

Disable Secure Boot:

  1. Press F2 to enter BIOS during boot.
  2. Go to the Secure Boot menu:
    • Advanced > Boot > Secure Boot (in Visual BIOS)
    • Boot > Secure Boot (in Aptio V BIOS)
  3. Disable Secure Boot.
  4. Press F10 to save the changes and restart.

SATA Mode is set to Optane Mode in BIOS.

Legacy Boot isn't allowed when in Optane Mode.

Change the Chipset SATA Mode:

  1. Press F2 to enter BIOS during boot.
  2. Go to the SATA Mode setting:
    • Advanced > Devices > SATA > Chipset SATA Mode (in Visual BIOS)
    • Advanced > Storage > SATA Mode Selection (in Aptio V BIOS)
  3. Set SATA Mode to either RAID or ACHI:
    • RAID if you plan to implement RAID
    • AHCI if you don't plan to use RAID
  4. Press F10 to save the changes and restart.

Warning: The operating system might not boot if this setting is changed after the operating system has been installed.

1To find out if your Intel NUC has the Visual BIOS or the AptioV BIOS, see BIOS Settings Glossary for Intel® NUC.

 

Related topic
Modern Standby (Microsoft site)