Fedora 20/21 installation image automatically boot in EFI mode when EFI is supported by the computer.
Most computers now support both EFI/BIOS boot, but some do have broken EFI,
e.g. older MACs.
The problem: installation starts in EFI mode, finish OK, but result in non-working system.
The problem: there is no way to force Fedora image to force boot in BIOS mode.
So I have to take the disk out, install Fedora (from the same installation image) on a computer non-supporting EFI, then put the disk back, and everything works fine.
It would be extremely convenient to have an option to select boot method: EFI or BIOS during boot from image, when EFI is supported. Automatic priority to EFI if EFI is supported is not good because EFI is often broken.
You need to force your firmware to boot in CSM mode if that's what you want. Forcing a BIOS install on a UEFI system (or some half-baked broken system) is just bound to end up in misery and more bugs.