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At boot time, all BIOS services are available, and the memory below address 0x00400 contains the interrupt vector table. BIOS POST has initialized the system timers, interrupt controller(s), DMA controller(s), and other motherboard/chipset hardware as necessary to bring all BIOS services to ready status.
Parts of coreboot becomes the systems BIOS and stays resident in memory after boot. Das U-Boot is a bootloader for embedded systems. It is used on systems that do not have a BIOS/UEFI but rather employ custom methods to read the bootloader into memory and execute it. Historical bootloaders, no longer in common use, include:
For a cold boot, for example, it may need to execute all of its functionality. If, however, the system supports power saving or quick boot methods, the BIOS may be able to circumvent the standard POST device discovery, and simply program the devices from a preloaded system device table.
BIOS interrupt calls perform hardware control or I/O functions requested by a program, return system information to the program, or do both. A key element of the purpose of BIOS calls is abstraction - the BIOS calls perform generally defined functions, and the specific details of how those functions are executed on the particular hardware of the system are encapsulated in the BIOS and hidden ...
The video BIOS is almost always located in the memory segment beginning at C0000h, the start of the memory area reserved for option ROMs; this is because when the motherboard has a built-in VGA controller, the option ROM will reside in the BIOS – the BIOS knows where it is and shadows it into RAM at a fixed time.
Once all the boot and system drivers have been loaded, the kernel starts the session manager (smss.exe), which begins the login process. After the user has successfully logged into the machine, winlogon applies User and Computer Group Policy setting and runs startup programs declared in the Windows Registry and in "Startup" folders. [5]
It is located on fixed disks and removable drives, and 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 — or even less, when additional features like more than ...
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.