How Is Flash BIOS Written to RAM?
Flashing BIOS refers to reprogramming the BIOS EEPROM with special software. The reason to do this is to make adjustments to the hardware chips. EEPROM is normally not rewritten; after all, the RO in EEPROM stands for "read-only." However, changes can be added to the chip to improve performance at bootup, such as adding new features, bug fixes or support for new hardware. Flashing BIOS to RAM involves using shadow flash to "burn" instructions from ROM into RAM.
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BIOS
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BIOS memory chips BIOS, or basic input/output system, is built-in computer software that resides on the chips that determine what a computer can do without loading data from a disk. It operates at bootup, and tells the computer what components it has, such as the keyboard, the monitor, memory and the hard drive.
The BIOS is on a ROM, or read-only memory, chip built into the computer. This guarantees the BIOS will always be available and will not have problems due to disk hardware failures. It also allows a computer to boot itself in a process known as shadowing.
EEPROM
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Memory chips Electrically Erasable Programmable Read-Only Memory (EEPROM) is a special kind of programmable memory. Exposing the programmable memory to an electrical charge can erase it. Its main feature is that EEPROM retains its memory contents even when there is no electrical power. Like other types of ROM, EEPROM does not operate as fast as RAM, and is similar to flash memory. The difference is that EEPROM writes and erases data one byte at a time. Flash memory, on the other hand, allows data to be erased or written in blocks, which allows for faster function.
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ROM BIOS Shadow Function
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BIOS memory chips The shadowing process means the BIOS transfers data from the ROM chip to RAM's "high memory" that lies between 640K and 1024K. This is an area of memory reserved for BIOS data that is now on the RAM chip.
The problem that now occurs is that BIOS is typically only used at the very beginning of the boot process, and hardly ever after that. Modern operating systems and their drivers and libraries handle everything; thus, ROM shadowing presents little performance gain.
Hazards of BIOS Flashing
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BIOS Chip The BIOS is the most critical component on the computer since it is the first program that runs when you turn on the machine. Without the BIOS, the machine cannot boot. A BIOS upgrade must be properly performed. Failure can permanently ruin the BIOS, making the computer a boat anchor. Some common reasons for BIOS flashes gone bad are flashing the BIOS with an incorrect BIOS version and a power failure during the flashing process.
Flash BIOS Written to RAM
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Flash BIOS Two files are needed to update a flash BIOS. One is a binary file that contains the BIOS code, and the second is a program called a loader. The loader connects to the motherboard circuitry. It then transfers the binary contents of the BIOS file to the RAM chips.
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References
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