- Ability to boot from large disks (over 2 TiB)
- Faster boot-up
- CPU-independent architecture
- CPU-independent drivers
- Flexible pre-OS environment, including networking support
- Modular design
Disk support
In addition to the standard PC disk partition scheme, which uses a master boot record (MBR), EFI adds support for a new partitioning scheme: GUID Partition Table (GPT). GPT does not suffer from many of the limitations of MBR. In particular, the MBR limits on the number and size of disk partitions (up to 4 partitions per disk, up to 2.2 TB (2.2 × 1012 bytes) per disk) are relaxed. GPT allows for a maximum disk and partition size of 9.4 ZB (9.4 × 1021 bytes). The EFI specification does not prescribe any particular file system. The only Microsoft Windows versions that can boot from disks larger than 2.2 TB, are 64-bit Windows Vista/7, Windows Server 2008 and later, as well as the Itanium versions of Windows Server 2003 and Windows XP.
Processor support
As of version 2.3, processor bindings exist for Itanium, x86, x86-64, and ARM.
The BIOS is limited to a 16-bit processor mode and 1 MB of addressable space due to the design being based on the IBM 5150 which used the 16-bit Intel 8088. In comparison, the UEFI processor mode can be either 32-bit (x86-32, ARM) or 64-bit (x86-64 and Itanium). 64-bit UEFI supports long mode which allows applications in the pre-boot execution environment to have direct access to all of the memory using 64-bit addressing.
UEFI requires the firmware and operating system to be size-matched, e.g. a 64-bit UEFI implementation can only boot a 64-bit UEFI operating system.