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Nonvolatile BIOS memory refers to a small memory on PC motherboards that is used to store BIOS settings. It is traditionally called CMOS RAM because it uses a volatile, low-power complementary metal–oxide–semiconductor (CMOS) SRAM (such as the Motorola MC146818 [1] or similar) powered by a small battery when system and standby power is off. [2]
During the POST, the BIOS must integrate multiple competing, changing, and even mutually exclusive standards and initiatives for the matrix of hardware and operating systems the PC is expected to support, although at most only simple memory tests and the setup screen are displayed. The principal duties of the main BIOS during POST include:
The actual key depends on specific hardware. The settings key is most often Delete (Acer, ASRock, Asus PC, ECS, Gigabyte, MSI, Zotac) and F2 (Asus motherboard, Dell, Lenovo laptop, Origin PC, Samsung, Toshiba), but it can also be F1 (Lenovo desktop) and F10 . [50] Features present in the BIOS setup utility typically include:
However, BIOS manufacturers and OEMs have relied on SMM for newer functionality like Advanced Configuration and Power Interface (ACPI). [9] [10] Some uses of the System Management Mode are: Handle system events like memory or chipset errors; Manage system safety functions, such as shutdown on high CPU temperature; System Management BIOS (SMBIOS)
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 ...
An option ROM for the PC platform (i.e. the IBM PC and derived successor computer systems) is a piece of firmware that resides in ROM on an expansion card (or stored along with the main system BIOS), which gets executed to initialize the device and (optionally) add support for the device to the BIOS.
INT 10h is fairly slow, so many programs bypass this BIOS routine and access the display hardware directly. Setting the video mode, which is done infrequently, can be accomplished by using the BIOS, while drawing graphics on the screen in a game needs to be done quickly, so direct access to video RAM is more appropriate than making a BIOS call ...
CMOS inverter (a NOT logic gate). Complementary metal–oxide–semiconductor (CMOS, / ˈ s iː m ɒ s /, also US: /-ɔː s / [1]) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSFETs for logic functions. [2]