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Unlike the legacy PC BIOS, UEFI does not rely on boot sectors, defining instead a boot manager as part of the UEFI specification. When a computer is powered on, the boot manager checks the boot configuration and, based on its settings, then executes the specified OS boot loader or operating system kernel (usually boot loader [ 62 ] ).
Unified Extensible Firmware Interface (UEFI) is a successor to the legacy PC BIOS, aiming to address its technical limitations. [5] UEFI firmware may include legacy BIOS compatibility to maintain compatibility with operating systems and option cards that do not support UEFI native operation.
The Video BIOS provides some basic display services for BIOS and operating systems, for example INT 10H (Legacy BIOS), VBE (Legacy BIOS) and UEFI GOP. The original IBM PC BIOS included integrated support for the IBM CGA and MDA video adapters (and did not support option ROMs at all), so those video cards had no option ROMs.
The BIOS boot partition is a partition on a data storage device that GNU GRUB uses on legacy BIOS-based personal computers in order to boot an operating system, when the actual boot device contains a GUID Partition Table (GPT). Such a layout is sometimes referred to as BIOS/GPT boot.
To develop and implement UEFI (Unified Extensible Firmware Interface). The specification replaces BIOS as the software interface between your computer's hardware and OS, doing away with several ...
The first stage of PC boot loaders (FSBL, first-stage boot loader) located on fixed disks and removable drives must fit into the first 446 bytes of the master boot record in order to leave room for the default 64-byte partition table with four partition entries and the two-byte boot signature, which the BIOS requires for a proper boot loader ...
UEFI provides backward compatibility with legacy systems by reserving the first block (sector) of the partition for compatibility code, effectively creating a legacy boot sector. On legacy BIOS -based systems, the first sector of a partition is loaded into memory, and execution is transferred to this code.
For this reason, later BIOS implementations may use a small portion of BIOS flash ROM as NVRAM, to store setup data. [7] Today's UEFI motherboards use NVRAM to store configuration data (NVRAM is a portion of the UEFI flash ROM), but by many OEMs' design, the UEFI settings are still lost if the CMOS battery fails. [8] [9]