FreeDOS Boot File – My BIOS Requires Exact File

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Problem :

Dell’s Alienware BIOS requires that you specify an EXACT FILE before allowing you to add a bootable entry (what a pita, but that’s a different matter). Anyhow, I don’t know that much about the boot sequence of the old DOS or of FreeDOS, so I am trying to figure out what file to point it to. Most of the ones I have tried so far have led to “Selected boot device failed. Press any key to reboot the system”.

I think it is looking for some type of EFI file/partition, but I have set it to legacy so it should boot.

Solution :

BIOS and UEFI are completely different types of firmware to boot the system

  • BIOS is absolutely dumb and just loads the first sector on the boot disk (MBR) and run it. It knows nothing about booting the OS. It’s the job of the bootloader on the MBR to do that
  • UEFI OTOH knows a lot about file systems and many things, and load PE executables in the ESP to boot

You can’t boot DOS from UEFI because UEFI can only load a PE executable of the same bitness, and there’s no 64-bit DOS. A few low-cost machines (mainly Atom CPUs) have 32-bit UEFI but there’s no 32-bit DOS either

If there’s CSM in your UEFI then you can switch back to that legacy “BIOS” mode and boot DOS, but then the location of boot files depends on the bootloader requirement and BIOS doesn’t care about that as I said

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