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Throughout the internet, you can see an UEFI/BIOS Boot Mode option (or something similar) present in the BIOS, so one can switch between UEFI and Legacy BIOS mode.

I don't have this option.

This is what my Boot section looks like: enter image description here

Boot Option Priorities

Boot Option #1           [ubuntu (PO: ST2000v...]
Boot Option #2           [ubuntu (PO: ST2000V...]
Boot Option #3           [boot (PO: ST2000VMO...]
Boot Option #4           [UEFI OS (PO: ST2000...]
Boot Option #5           [UEFI OS (PO: ST2000...]
Boot Option #6           [PO: ST2000VM003-1CT...]
Boot Option #7           [UEFI: Built-in EFI ...]

As you can see, there's no option to change boot mode.

Secure boot, which is under Security, is disabled (I've heard that it should be disabled if you want that option). Still, I can't find the option to change the boot mode, so I'm not sure what that means.

Do I have to change another setting for it to appear? Do I only have one boot mode? In that case, how may I find out which one I have? Do I have both but can't change it in the BIOS? In that case, can I still change it in some other way?

Basically: How do I find out what's my board's boot mode(s), and how do I change the mode when there's no option available?

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  • 1
    What's your hardware? What are you trying to achieve?
    – gronostaj
    Commented May 25, 2022 at 13:49
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    Is your disk partitioned as MBR or GPT? Windows cannot boot from MBR under UEFI, nor can it boot from GPT under BIOS. What that means is if you have a GPT boot disk then your system is UEFI, if your boot disk is MBR then you have "legacy" BIOS
    – Mokubai ♦
    Commented May 25, 2022 at 13:53
  • @gronostaj My board is a PCWARE IPX1800G1, and I'm trying to achieve exactly what my question stated: Find out the boot modes that I have available, the one that I'm currently in, and change them if possible.
    – Luiz Martins
    Commented May 25, 2022 at 14:00
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    @LuizMartins - That is correct. Modern Intel and AMD systems are going away from supporting it for a variety of reasons, one of those reasons, is the operating system with the largest share no longer supports Legacy Boot. While Windows 10 supports it, Windows 11 does not support MBR, and support for Windows 10 will end in 2025. You provided no information on the hardware, but based on the display boot orders, it doesn't appear you have hardware that doesn't support booting MBR (i.e. Legacy Mode).
    – Ramhound
    Commented May 25, 2022 at 14:24
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    @LuizMartins - Your device's firmware is UEFI. It likely does not have a Legacy Mode but a single mode that supports both UEFI and Legacy. My comment was to point out that newer devices are dropping the Legacy Mode all together.
    – Ramhound
    Commented May 25, 2022 at 15:07

4 Answers 4

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Throughout the internet, you can see an UEFI/BIOS Boot Mode option (or something similar) present in the BIOS, so one can switch between UEFI and Legacy BIOS mode.

The implementation of this feature varies. More often, you don't actually switch between the two modes exclusively – instead the offered modes are more like "UEFI only" and "UEFI or legacy both". (That is, the firmware remains the same and never loses its UEFI functionality, it just either enables the additional BIOS-compatibility module or not.)

So it's possible that some firmwares offer "both UEFI & legacy" as their only mode of operation (that is, both the UEFI support and the BIOS compatibility parts are permanently active). This is less common in new systems, where disabling legacy boot allows for a lot of optimizations, but used to be quite common in older systems.

This seems to be your situation; you have #6 as a "legacy BIOS bootsector" option (as well as the whole "BBS Priorities" section) among various UEFI-based options.

Do I have to change another setting for it to appear? Do I only have one boot mode? In that case, how may I find out which one I have? Do I have both but can't change it in the BIOS? In that case, can I still change it in some other way?

Just reorder the offered boot options – for example, if you choose "P0: [disk]" as the first option, it'll boot from the legacy BIOS sector; if you choose "ubuntu", it'll boot from the configured UEFI bootloader file (according to EFI NVRAM); etc. This also applies to the F8 boot menu. For bootable USB sticks, usually you will also have two similar options, one for BIOS and the other for UEFI.

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  • I've always wondered why I had some repeated boot selections, now it makes sense! Thanks for the answer!
    – Luiz Martins
    Commented May 25, 2022 at 15:13
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    That's not the only reason – options #1/2/3 look legitimately duplicate (probably for different operating systems; use efibootmgr to clean them up). I'm not sure why you have #4 and #5 for the same thing, either (though it might be the same option listed twice in the BootOrder variable).
    – grawity_u1686
    Commented May 25, 2022 at 15:15
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Your boot options #1 - #2 have an OS name (a free-form text) associated with them, which is only possible with UEFI. Option #3's boot is probably similar.

Boot options #4, #5 and #7 clearly indicate that they are UEFI. But boot option #6 just specifies a disk and has no UEFI indicator, so it is probably a legacy BIOS-style boot option. If that's true, then your system clearly supports both boot modes, which would be expected given the firmware copyright year of 2013 (see the top of the image).

The fact that you have Secure Boot as a configurable option confirms it: it is impossible to have Secure Boot without UEFI. On some systems, enabling Secure Boot will also lock out/disable/hide legacy boot options, enforcing UEFI boot only. But back in 2013, designing an UEFI-only x86 system without legacy BIOS compatibility would have been an odd choice.

If there is indeed no way to choose a "UEFI only" or a "legacy-only" mode, you must be extra careful when booting your OS installer: if the installation media is compatible with both UEFI and legacy BIOS boot, you should see two boot options for that media, one with UEFI and the other without. You should choose the boot mode of the OS installer to match the intended boot mode of the OS installation.

Note that the "UEFI/legacy/both boot modes allowed" selection does not necessarily have to be in the Boot section of the BIOS menus (although that would be a sensible place for it). It might also be buried deep somewhere in the "advanced options" section.

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How do I find out what's my board's boot mode(s)?

Your screenshot already shows that your motherboard has UEFI and Legacy capabilities.

Do you see your the Boot Option Priorities on your screenshot? It shows 7 devices, some UEFI and some not. The same physical devices are listed more than once, because you have the option to boot them as UEFI or as Legacy.

Sow do I change the mode when there's no option available?

You may reorder these devices on the list so that, for the same physical device, your motherboards access it as UEFI or legacy first.

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it depend options offered by Bios firmware, Some Large integrators Like Lenovo unfortunately followed intel and Microsoft recommandations for security raisons and have deleted CSM & Legacy Modules ! but mainly have Phoenix's Technologie Bioses. you do have Megatrends one, i think it offers you more options Oddly Some modern models still have it though

Disable first Secure Boot Then go to the last tab (Startup) you should find there the "OS Optimized defaults" option in "Load Setup Defaults" , disable it ! then return to Boot Tab you should see the Uefi/Legacy appears

Hope it helps Dave

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