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I've not enough reputation points to comment on this (outdated) question and it has no answers, I am aware of that one existing: Bootloaders - Booting an MBR only OS using a UEFI only BIOS

After 8 years I'd like to bring on the topic again because now I've very much the same problem. I use Easy2Boot as a often recommended multiboot solution and so far I am very happy with it. But despite UEFI exists for a decade now, many live images still doen't support UEFI-Only systems, not to mention the bootloaders for old OSs'.

All solutions I tried so far were in vain for my .ISOs:

  • Secure Boot is disabled all the time
  • Formatted active USB partiton to FAT32 instead of NTFS
  • Searched for CSM/BIOS support in firmware (no option)
  • Used another .ISO download source
  • Used Ventoy/Yumi as alternative multiboot instead
  • Used Rufus/ImgBurn/UltraISO as alternative single-boot instead
  • Used special folders Easy2Boot provided
  • Tried another USB port.
  • Did research about Clover and other things online (but they provide the opposite way only - I don't want to have UEFI from within BIOS, just the contrary)

It would do the trick too if I'd be able to get Easy2Boot loading legacy E2B menu instead of agFM on said UEFI-only systems successfully. That menu is able to boot them (almost) all.

Example ISOs that suffer from the issue:

  • EasyRE for Windows XP/7/10
  • Windows XP Setup Image
  • Testdisk
  • Tenorshare Windows Boot Genius
  • TrendMicro Rescue Disk
  • Some other antivirus images

Does anyone know a solution/workaround to get Easy2Boot or any other (multi)boot loader to boot BIOS/CSM images (.ISO) from within UEFI-only computers (that lacks of optional CSM compatibility options)?

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    Unless the mb has CSM Mode, there isn't a way except within a VM, since UEFI [64bit] emulates BIOS [16bit] within a 32bit environment, none of which is controllable once the UEFI firmware hands off to the bootloader. CSM Mode had one sole purpose - to allow the booting of distros that didn't yet support EFI boot circa <2017 - that is literally the only reason why it existed and is why motherboard OEMs began phasing it out of their firmware several years ago. Devs have to update their boot ISOs or newer ones have to be used, like Hiren BootCD PE
    – JW0914
    Commented Mar 3 at 16:12
  • Thanks, yes I heard about that. But maybe it changed in the last years and someone developed a software to do so. If there would exist a chance to load BIOS from withi UEFI, then I'd be very interested in.
    – Dragodraki
    Commented Mar 3 at 16:17
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    AFAIK, highly unlikely since the reason why CSM Mode exists hasn't been applicable since 2017 and will never be applicable again - it's a feature with zero purpose beyond accessing legacy OPROMs. It's the motherboard's firmware that emulates BIOS' 16bit architecture within a 32bit environment (a VM does so via the hypervisor). AFAIK, what's asked simply isn't possible because it's the firmware itself, not an application or bootloader, that controls whether the firmware itself supports emulating BIOS' 16bit architecture within a 32bit environment (doing so causes performance degradation)
    – JW0914
    Commented Mar 3 at 16:36
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    Is this a duplicate of superuser.com/q/1788579/1686?
    – grawity_u1686
    Commented Mar 3 at 20:41
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    @Dragodraki: For Linux, there's an answer from a ventoy developer about converting legacy ISO to UEFI at this post.
    – harrymc
    Commented Mar 3 at 21:13

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