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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 ...
Unwanted BIOS reset may be avoided by replacing the battery cell with the PSU power switch turned on and plugged into an electric wall socket. On ATX motherboards, the PSU will supply 5V standby power to the motherboard to keep CMOS memory energized while the system is off.
The BIOS also updates the ESCD each time the hardware configuration changes, after deciding how to re-allocate resources like IRQ and memory mapping ranges. After the ESCD has been updated, the decision need not be made again, which thereafter results in faster startup without conflicts until the next hardware configuration change.
In a PC, the BIOS, pre-loaded in ROM on the motherboard, takes control immediately after the CPU is reset, including during power-up, when a hardware reset button is pressed, or when a critical software failure (a triple fault) causes the mainboard circuitry to automatically trigger a hardware reset. The BIOS tests the hardware and initializes ...
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 .
Many PC motherboard suppliers licensed the BIOS "core" and toolkit from a commercial third party, known as an "independent BIOS vendor" or IBV. The motherboard manufacturer then customized this BIOS to suit its own hardware. For this reason, updated BIOSes are normally obtained directly from the motherboard manufacturer.
The southbridge typically implements the slower capabilities of the motherboard in a northbridge-southbridge chipset computer architecture. In systems with Intel chipsets, the southbridge has been named I/O Controller Hub (ICH) and later replaced by Platform Controller Hub chipsets. In older Intel/AMD architectures the southbridge is usually ...
As such, the MRC is a part of the BIOS (or firmware) of an Intel motherboard. George Chen, a research and development (R&D) director at ASUS, described it in 2007 as follows: [1] The MRC is part of reference BIOS code, which relates to memory initialization in the BIOS.