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This implies that after the hardware reset, the CPU will start execution at the physical address 0xFFFF0. In IBM PC compatible computers, This address maps to BIOS ROM. The memory word at 0xFFFF0 usually contains a JMP instruction that redirects the CPU to execute the initialization code of BIOS. This JMP instruction is absolutely the first ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 2 December 2024. Restoring the software of an electronic device to its original state For the Tilian Pearson album, see Factory Reset (album). A factory reset, also known as hard reset or master reset, is a software restore of an electronic device to its original system state by erasing all data ...
The BIOS uses the boot devices set in Nonvolatile BIOS memory , or, in the earliest PCs, DIP switches. The BIOS checks each device in order to see if it is bootable by attempting to load the first sector (boot sector). If the sector cannot be read, the BIOS proceeds to the next device.
The BIOS begins its POST when the CPU is reset. The first memory location the CPU tries to execute is known as the reset vector . In the case of a hard reboot , the northbridge will direct a code fetch request to the BIOS located on the system flash memory .
In computing, the reset vector is the default location a central processing unit will go to find the first instruction it will execute after a reset. The reset vector is a pointer or address , where the CPU should always begin as soon as it is able to execute instructions.
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 ...
Many BIOS updates also include upgrades for the embedded controller firmware. An embedded controller is sometimes known as a "Keyboard Controller BIOS", which comes from the fact that the embedded controller evolved from the keyboard controller and often still is used as a keyboard controller.
It is referred to as non-volatile memory or NVRAM because, after the system loses power, it does retain state by virtue of the CMOS battery. When the battery fails, BIOS settings are reset to their defaults. The battery can also be used to power a real time clock (RTC) and the RTC, NVRAM and battery may be integrated into a single component.