Translations:Handbook:AMD64/Blocks/Disks/20/en

Some buggy BIOSes or EFIs configured to boot in BIOS/CSM/legacy mode might also have problems with booting from GPT labeled disks. If that is the case, it might be possible to work around the problem by adding the boot/active flag on the protective MBR partition which has to be done through  with the   option to force it to read the partition table using the MBR format.