UEFI
The Unified Extensible Firmware Interface, or UEFI, is a standard firmware interface for the personal computer. It is designed to replace BIOS (basic input/output system). This standard was created by over 140 technology companies as part of the UEFI consortium, including Microsoft. All 64-bit versions of PCs running Windows with a logo from the Windows Certification Program will use UEFI instead of BIOS. UEFI is designed to improve software interoperability and address limitations of BIOS. Some advantages of UEFI firmware include:
- Better security by helping to protect the pre-startup—or pre-boot—process against bootkit attacks.
- Faster startup times and resuming from hibernation.
- Support for drives larger than 2.2 terabytes (TB).
- Support for modern, 64-bit firmware device drivers that the system can use to address more than 17.2 billion gigabytes (GB) of memory during startup.
- Capabililty to use BIOS with UEFI hardware.
BIOS is considered firmware while UEFI is a programmable software interface that sits on top a computer’s hardware and firmware. UEFI sits on top of the system BIOS. Rather than all of the boot code being stored in the motherboard’s BIOS, UEFI sits in the "EFI" directory in non-volatile memory; either in NAND on the motherboard, on your hard drive, or in some cases on a network share.
Most UEFI firmware images provide legacy support for BIOS services. UEFI can support remote diagnostics and repair of computers, even without another operating system installed. A normal PC 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. The UEFE processor mode can be either 32-bit (x86-32, AArch32) or 64-bit (x86-64, Itanium, and AArch64).
In addition to the standard PC disk partition scheme, which uses a master boot record (MBR), UEFI works with a new partitioning scheme called GUID Partition Table or GPT. GPT allows for a maximum disk and partition size of 8 ZB whereas the MBR limits the number or partitions to four and size to 2 TB.
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