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The boot code in the VBR can assume that the BIOS has set up its data structures and interrupts and initialized the hardware. The code should not assume more than 32 KB of memory to be present for fail-safe operation; [1] if it needs more memory it should query INT 12h for it, since other pre-boot code (such as f.e. BIOS extension overlays, encryption systems, or remote bootstrap loaders) may ...
In Microsoft Windows, the MBR boot code tries to find an active partition (the MBR is only 512 bytes), then executes the VBR boot code of an active partition. The VBR boot code tries to find and execute the bootmgr file from an active partition. [3] On systems with UEFI firmware, UEFI invokes bootmgfw.efi from an EFI system partition at startup ...
In computing, the BIOS parameter block, often shortened to BPB, is a data structure in the volume boot record (VBR) describing the physical layout of a data storage volume. On partitioned devices, such as hard disks , the BPB describes the volume partition, whereas, on unpartitioned devices, such as floppy disks , it describes the entire medium.
Note: The column MBR (Master Boot Record) refers to whether or not the boot loader can be stored in the first sector of a mass storage device. The column VBR (Volume Boot Record) refers to the ability of the boot loader to be stored in the first sector of any partition on a mass storage device.
The boot ROM is either placed on the same die as the CPU or is an external ROM chip. On modern systems, the boot ROM (whether integrated into CPU or external ROM chip) is usually use NOR flash which supports execute in place. The boot ROM will then initialize the hardware busses and peripherals needed to boot.
The partition type (or partition ID) in a partition's entry in the partition table inside a master boot record (MBR) is a byte value intended to specify the file system the partition contains or to flag special access methods used to access these partitions (e.g. special CHS mappings, LBA access, logical mapped geometries, special driver access, hidden partitions, secured or encrypted file ...
On Apple Mac computers using Intel x86-64 processor architecture, the EFI system partition is initially left blank and unused for booting into macOS. [13] [14]However, the EFI system partition is used as a staging area for firmware updates [15] and for the Microsoft Windows bootloader for Mac computers configured to boot into a Windows partition using Boot Camp.
Since Windows NT 3.1 (the first version of Windows NT), [4] Microsoft has defined the terms as follows: The system partition (or system volume) [5] is a primary partition that contains the boot loader, a piece of software responsible for booting the operating system. [6]: 1087 This partition holds the boot sector and is marked active. [7]: 970