I am trying to install Linux and I need to use legacy BIOS mode. I tried the common method shown on the manufacturer's support page, but the UEFI/legacy setting seems to be disabled on my PC. The Bot Mode row is black. I cannot select it with up down keys.

How can I enable the UEFI/legacy option?

If it helps, my PC is Lenovo Ideapad S340IIL and Intel RST is enabled on it.

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  • 1
    Your other computer supported CSM, your new computer, does not. Windows 8.1 was almost released 10 years ago. Every major OS supports UEFI.
    – Ramhound
    Sep 13, 2021 at 16:40
  • 1
    All major Linux distributions support UEFI.
    – Ramhound
    Sep 13, 2021 at 16:46
  • 1
    You typically have to update UEFI and turn off Intel RST/Optane. But if dual booting with Windows first install AHCI driver into Windows or it will not work. askubuntu.com/questions/1144049/… & superuser.com/questions/1672500/…
    – oldfred
    Sep 13, 2021 at 19:00
  • @oldfred - In this case the author’s hardware doesn’t support CSM/Legacy Boot
    – Ramhound
    Sep 14, 2021 at 11:49
  • Does not matter if UEFI or BIOS, still need to turn off RST. And always good idea to make sure you have latest UEFI firmware & if SSD latest SSD firmware. Another Lenovo, may be similar? askubuntu.com/questions/1291280/…
    – oldfred
    Sep 14, 2021 at 14:32

1 Answer 1


How can I enable the UEFI/legacy option?

You cannot. Your hardware does not support Compatibility Support Module (CSM). Your device has a 10th generation Intel Core processor, per Intel's announcement in July 2020, your processor was only validated to support UEFI.

Intel previously announced that in 2020 they are phasing out support for legacy Basic Input/Output System (BIOS) boot mode. This means that many of the Lenovo products launching in 2020 will no longer support the Legacy Boot option in BIOS. The only Boot option that will be supported on those products is Unified Extensible Firmware Interface (UEFI).

Applicable Brands:

  • ThinkStation
  • ThinkCentre
  • ThinkPad
  • ThinkBook
  • Lenovo
  • ideacentre
  • ideapad

Source: Legacy BIOS Boot Support Removed in Lenovo 2020 products

Intel Announcement: Legacy BIOS Boot Support Removal for Intel Platforms Technical Advisory

Starting with client platforms launching in 2020. Intel will no longer be supporting legacy Basic Input/output System (BIOS) mode.

  • This Includes 10th generation Intel platforms launching in 2020 and all future platforms.
  • @AbdullahBaig - Your PC most definitely DOES NOT support Legacy mode. As for the reason Boot Mode option is still present in the list of options, I have no idea, I just assume the developers are lazy. If it supported Legacy Boot/CSM/Compatibility Mode you would have been able to change the Boot Mode.
    – Ramhound
    Sep 13, 2021 at 16:44
  • Thanks a lot for the explanation. I understand the situation now. The notion that my PC does not support Legacy mode is based on the switch option greyed out in the Boot menu and the manufacturer's announcement. This makes it highly likely to be true. But is there a setting or a status check in my PC which I can check and be 100 % sure about it? That would help me to have full closure on this issue.
    – paki eng
    Sep 13, 2021 at 16:52
  • @AbdullahBaig - I have no idea what you are looking for, I have provided the announcement that indicates, that 10th generation Intel Core processors were only validated to support UEFI mode.
    – Ramhound
    Sep 13, 2021 at 16:53
  • Thanks. Yeah, the 10 gen processor nails it.
    – paki eng
    Sep 13, 2021 at 16:57
  • It is entirely possible that whatever motherboard the manufacturer makes could somehow be designed to support 9th and 10th generation processors. Having that option available would allow the supported group to use it.
    – Mokubai
    Sep 13, 2021 at 17:23

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