Support for legacy boot is slowly being eliminated. It is costly, insecure and completely unnecessary. All modern operating systems, including every full-featured Linux distribution, can support UEFI boot and do not require legacy boot.
n_scott_pearson, thank you for your reply.
Please allow me to follow up.
I have a computer (Asrock Deskmini H470) that exhibits the following behavior:
If I install Intel 10th gen cpu G6400: I can enable CSM, and then see options to boot USB from legacy / UEFI
If I install Intel 11th gen cpu i9-11900: CSM still appears in menu, and you can try to enable it, but upon boot CSM reverts back to disabled, and options to boot USB from legacy / UEFI never appear.
Based on what you are saying, this is a bug in the manufacturer's BIOS, and NOT any difference in the Intel 11th gen chip vs the previous generation.
Are you 100% sure this is correct, or is it possible that the 11th gen i9-11900 has some kind of change that makes switching CSM on and booting from legacy USB impossible?
Yes, I am sure. It is the BIOS that is responsible for this feature and its support. I have no idea why the BIOS would disable the feature; this is something that you will need to discuss with Asrock.
Now, that said, you do understand that a generational change in processor could require that you reinstall your O/S, right? I always reinstall the O/S if the processor/chipset changes. Of course, the issue of boot from USB is purely the BIOS if only the processor is changing.
If that's the case, it's news to me. I deal mostly with the NUCs and the latest models purposely do not support Legacy Boot, so I really cannot say. I could almost (but still a teeny bit skeptical) believe that iGFX support is only available as a UEFI driver (and not as a Legacy Video BIOS). Regardless, Intel Customer Support (@Ronny_G_Intel?) will need to verify this for us both...
Sorry for the delay in responding back, it has been difficult for me to cope with the workload.
This issue is posted under <Intel® Desktop Boards> which is not monitored by Intel Customer Support because this product line considered legacy. Allow me to move this post over the Processors Community so that it is properly handled by the CPU team.