Legacy BIOS Boot Mode and UEFI Boot Mode Oracle® X4 Series Servers Administration Guide (2024)

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Legacy BIOS Boot Mode and UEFI Boot Mode

Your system is equipped with UEFI BIOS, which is based on the Unified Extensible Firmware Interface (UEFI) specification.

UEFI BIOS offers advantages over legacy versions of BIOS, but the way it boots is not compatible with some operating systems, and it might not be the best choice for some configurations. For this reason, the system can be configured to boot in Legacy BIOS Boot Mode or UEFI Boot Mode. Legacy BIOS Boot Mode is the default.

Normally, you set the boot mode only once, before installing the operating system. Once you have installed the operating system, if you change the boot mode, you cannot boot the operating system.

See your installation guide for a list of the operating systems that support UEFI boot mode.

When to Select Legacy or UEFI BIOS Boot Mode

When the option is available to choose between Legacy BIOS Boot Mode or UEFI Boot Mode, the advantages of UEFI Boot Mode include:

• Boots faster.

• Avoids legacy option ROM address constraints. For more information, see Other BIOS Boot Mode Considerations.

• Supports operating system boot partitions greater than 2 terabytes (2 TB). For more information about limitations for supported operating systems, refer to your server product notes.

• Integrates PCIe device configuration utilities with BIOS Setup Utility menus.

• Displays bootable operating system images in the boot list as labeled entities. For example, it displays Windows boot manager labels instead of raw device labels.

• Provides efficient power and system management.

• Includes robust reliability and fault management.

• Uses UEFI drivers.

Choose Legacy BIOS Boot Mode:

• If your operating system does not support booting in UEFI Boot Mode

• To allow HBAs and Express Module devices to use option ROM

Other BIOS Boot Mode Considerations

Choosing Legacy BIOS Boot Mode allows HBAs and Express Module devices to use option ROMs. Choosing UEFI Boot Mode uses UEFI drivers.

Only devices that support the selected boot mode are listed on the BIOS Boot screen. If you select UEFI Boot Mode, only boot candidates that support UEFI BIOS Boot Mode are listed on the BIOS Setup Utility screens in the boot order list. If you select Legacy BIOS Boot Mode, only boot candidates that support Legacy BIOS Boot Mode are listed in the boot order list.

When you switch between Legacy BIOS Boot Mode and UEFI Boot Mode (in either direction), BIOS settings that affect the Boot Option Priority List settings are changed and the original settings are lost. If you intend to switch back, back up your BIOS configuration. See Backup, Restore, and Revert BIOS Settings (Oracle System Assistant 1.1).

See your server product notes for a list of the operating systems that support UEFI Boot Mode.

Some operating systems require Legacy BIOS Boot Mode, and some can work with either mode. However, once an operating system is installed, it must use the boot mode that was used during the installation.

Viewing and Changing the Boot Mode

You can view or set the boot mode on your server using the following interfaces:

• BIOS Setup Utility. You can use the BIOS Setup Utility to view or set the target boot mode. For further details, see Select UEFI Boot Mode or Legacy BIOS Boot Mode (BIOS).

• Oracle System Assistant. If you are installing an operating system using the Oracle System Assistant, you can view or set the target boot mode for your server on the Oracle System Assistant Install Operating System screen, as described in Install an Operating System (Oracle System Assistant).

• Oracle ILOM. You can view the boot mode from the Oracle ILOM SP CLI or web interface. To view the server's target boot mode from the Oracle ILOM SP web interface, click System Management > BIOS. Or, to view it from the Oracle ILOM SP CLI, type: show /System/BIOS.