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The keyboard works even if the BIOS keyboard service is not called; keystrokes are received and placed in the 15-character type-ahead buffer maintained by BIOS.) The boot program must set up its own stack, because the size of the stack set up by BIOS is unknown and its location is likewise variable; although the boot program can investigate the ...
The principal duties of the main BIOS during POST include: verify CPU registers; verify the integrity of the BIOS code itself; verify some basic components like DMA, timer, interrupt controller; initialize, size, and verify system main memory; initialize BIOS; pass control to other specialized extension BIOSes (if installed)
When Secure Boot is enabled, it is initially placed in "setup" mode, which allows a public key known as the "platform key" (PK) to be written to the firmware. Once the key is written, Secure Boot enters "User" mode, where only UEFI drivers and OS boot loaders signed with the platform key can be loaded by the firmware.
Function Keys are also heavily used in the BIOS interface. Generally during the power-on self-test, BIOS access can be gained by hitting either a function key or the Del key. In the BIOS keys can have different purposes depending on the BIOS. However, F10 is the de facto standard for save and exit which saves all changes and restarts the system.
In this example of dual booting, the user chooses by inserting or removing the DVD from the computer, but it is more common to choose which operating system to boot by selecting from a boot manager menu on the selected device, by using the computer keyboard to select from a BIOS or UEFI Boot Menu, or both; the Boot Menu is typically entered by ...
There are 3 ID string formats, the first for older AMIBIOS, and the second and third for the newer AMI Hi-Flex ("high flexibility") BIOS. [17] These latter are displayed when the Insert key is pressed during power-on self-test. [17] The original AMI BIOS did not encrypt the machine startup password, which it stored in non-volatile RAM. [18]
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 ...
A PBA environment serves as an extension of the BIOS, UEFI or boot firmware and guarantees a secure, tamper-proof environment external to the operating system as a trusted authentication layer. [2] The PBA prevents any operating system from loading until the user has confirmed he/she has the correct password to unlock the computer. [ 2 ]