Hi, Below are the difference between UEFI and Legacy: Unified Extensible Firmware Interface(UEFI) is the successor to BIOS. UEFI uses the GUID Partition Table (GPT) whereas BIOS uses the Master Boot Record(MBR) partitioning scheme. GPT and MBR are both formats specifying physical partitioning information on the hard disk. Below I have listed the difference: Max partition size in MBR is ~2TB whereas in UEFI it is ~9 ZetaBytes