Legacy Boot is Greyed Out in BIOS Setup

Documentation

Troubleshooting

000032529

09/22/2020

What are you seeing?
In BIOS Setup, the Legacy BIOS setting is grayed out and can't be enabled.

Why are you seeing it?
Modern Standby is enabled in the BIOS of the Intel® NUC. Legacy Boot isn't allowed when Modern Standby is enabled.

How to fix it.

  1. Determine if your NUC has Intel's 'Visual BIOS' or 'AptioV BIOS'. See this page for assistance in determining your BIOS type.
  2. Change the Sleep Type Support to Legacy S3 Standby instead of Modern Standby:
    For systems with Visual BIOS:
    1. Press F2 to enter BIOS Setup during boot.
    2. Go to Advanced > Power.
    3. In the Secondary Power Settings pane, change Sleep Type Support from Modern Standby to Legacy S3 Standby.

    For systems with Aptio V BIOS:
    1. Press F2 to enter BIOS during boot.
    2. Click Power > Secondary Power Settings.
    3. Change the Sleep Type Support from Modern Standby to Legacy S3 Standby.

     
  3. Enable Legacy Boot.
    For systems with Visual BIOS:
    1. Navigate to the Advanced Boot menu and click the check box for Legacy Boot.

    For Systems with AptioV BIOS:
    1. Navigate to the Boot menu.
    2. Click the link for Boot Priority.
    3. Click the check box for Legacy Boot.

     
  4. Press F10 to save the changes and restart.

Additional information

At the next POST after changing this BIOS setting, the following warning appears:

WARNING! A change has been detected in the BIOS Sleep Type support setting, from <<last sleep type>> to <<desired 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.

Press Y to continue. (Background: According to Microsoft, switching the power model is not supported in Windows without a complete OS reinstall. Changing this BIOS setting does NOT change Windows power model.)

Related topic
Modern Standby (Microsoft site)