Loading and validating bios binary file
However, the need for a multi-stage boot process that requires loading multiple bootloaders is no longer necessary.
Our entire discussion thus far has focused on booting with the Intel PC-based architecture (which includes IA–32/IA–64 compatible architectures, such as those by AMD).
From that point onward, GRUB is out of the picture, Windows has no idea what happened, and the native Windows boot process takes over.
As 64-bit architectures emerged to replace 32-bit architectures, the BIOS was starting to look quite dated.
The first block of the VBR identifies the partition type and size and contains an Initial Program Loader (IPL), which is code that will load the additional blocks that comprise the second stage boot loader.
On Windows NT-derived systems (e.g., Windows Server 2012, Windows 8), the IPL loads a program called NTLDR, which then loads the operating system.
From this, the EFI boot loader identifies the EFI System Partition.
This system partition contains boot loaders for all operating systems that are installed on other partitions on the device.
Multiboot is a Free Software Foundation specification on loading multiple operating systems using a single boot loader.
The contents of the MBR are: Once the BIOS transfers control to the start of the MBR that was loaded into memory, the MBR code scans through its partition table and loads the Volume Boot Record (VBR) for that partition.
The VBR is a sequence of consecutive blocks starting at the first disk block of the designated partition.
For EFI-aware Windows systems, UEFI loads the , the EFI loader.
In general, even with UEFI, the dominant approach is to load an boot loader dedicated to a specific operating system rather than load that operating system directly.