How to create MBR-bootable (NOT UEFI!!) DD 12 64-bit ISO or USB
No matter what I try, I cannot seem to create an MBR-bootable DD 12 3270 64-bit media -- only the extremely UNWANTED UEFI media! This is unacceptable. Is there a solution?
Yup - boot it in MBR mode instead of UEFI mode. If it's unacceptable to boot in UEFI, you shouldn't be doing it.
It supports both, but if your motherboard supports UEFI will attempt to boot UEFI first in most cases. Use your one time boot menu / boot overrided menu and pick the non-UEFI mode.