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EEPROM is a chip that can be rewritten and erased by an electrical charge, used to save system settings in BIOS chips. It does not require a power source to maintain its data. Flash memory is faster and used for dynamic read/write requirements. Flash BIOS chips can use either EEPROM or flash memory.
EEPROM stands for Electrically Erasable Programmable Read Only Memory and is pronounced double-ee-prom or ee-prom. It’s a long name for a small chip that contains bits of data code that can be rewritten and erased by an electrical charge, one byte at a time. Your data cannot be selectively rewritten; the entire chip must be erased and rewritten to update its contents.
While RAM (Random Access Memory) loses its data every time you shut down your computer, EEPROM does not require a power source to maintain its data. For this reason, it is commonly used by many BIOS chips to save system settings.
BIOS stands for Basic Input/Output System. When a computer is turned on, the BIOS chip runs a program called CMOS (Complementary Metal Oxide Semiconductor) which contains settings that allow the computer to recognize its hardware. Users can enter the CMOS program during boot to change BIOS settings. Someone may need to do this, for example, when they get a new hard drive. After changing the settings, the BIOS will save the new copy of the instructions to EEPROM.
With the advent of EEPROM, manufacturers could also update the BIOS program itself. In the past this was not possible and an outdated BIOS chip meant having to replace the chip with a newer motherboard. A BIOS chip that can be updated using this feature is called a flash BIOS, because the EEPROM is updated using electrical charges or flashes.
EEPROM is slower than RAM, but it’s perfectly fine for applications like storing saved BIOS settings. It should not be chosen for applications with dynamic read/write requirements, such as a digital camera, memory stick, or flash card. For these purposes, a newer hybrid form called flash memory is used. Flash memory differs in that its data can be selectively rewritten. It can also be erased and rewritten in whole blocks, rather than one byte at a time. This makes it much faster than EEPROM.
Newer flash BIOS chips may or may not use flash memory, rather than EEPROM. The BIOS is just called a flash BIOS because the memory it uses, in both cases, is reprogrammed by flashing the chip, one byte at a time or in blocks.
