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The boot loader on the option ROM would attempt to boot from a disk, network, or other boot program source attached to or installed on the adapter card; if that boot attempt failed, it would pass control to the previous boot loader (to which INT 19h pointed before the option ROM hooked it), allowing the system to boot from another device as a ...
The Windows Boot Manager (BOOTMGR) is the bootloader provided by Microsoft for Windows NT versions starting with Windows Vista and Windows Server 2008. It is the first program launched by the BIOS or UEFI of the computer and is responsible for loading the rest of Windows. [1] It replaced the NTLDR present in older versions of Windows.
On Windows Vista and Windows 7, this can be fixed by configuring the msahci device driver to start at boot time (rather than on-demand). Setting non-AHCI mode (i.e. IDE or Combined mode) in the BIOS will allow the user to boot into Windows, and thereby the required registry change can be performed.
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]
When interrupt 19h is called, the BIOS attempts to locate boot loader software on a "boot device", such as a hard disk, a floppy disk, CD, or DVD. It loads and executes the first boot software it finds, giving it control of the PC. [28] The BIOS uses the boot devices set in Nonvolatile BIOS memory , or, in the earliest PCs, DIP switches.
In x86 computers, a first-stage bootloader is a compact 512-byte program that resides in the master boot record (MBR) and executes when a computer starts. Running in 16-bit real mode at address 0x7C00, it performs minimal hardware initialization, sets up a basic execution environment, and locates the second-stage bootloader.
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 ...