Physical Memory

Computer memory is divided into two categories: ROM and RAM. ROM ROM, read-only memory, consists of memory chips that contain programs that are acid-burned into the chips at the factory. The programs on a ROM chip (sometimes called firmware) are permanent; they cannot be changed. ROM stores system BIOS and startup BIOS programs in a microchip that does not lose data when the power is turned off. RAM RAM, random access memory, can be written to and read from by the CPU and some applications. It is stored on chips that are either socketed or soldered directly on the systemboard or housed on little mini-boards. Since RAM depends on power from the computer, all of the data in RAM is lost when the power is turned off.

EPROM

EPROM (erasable programmable ROM) chips have a special window that allows the current memory contents to be erased with a special ultraviolet light so that the chip can be reprogrammed. Many BIOS chips are EPROM chips. They are seen on the systemboard with shiny tape covering the window. EEPROM, EPROM, and ROM chips all provide BIOS that is not erasable during normal PC operations.

Some ROM chips reside on the systemboard and some on the expansion boards. These ROM chips contain the programming that the computer uses to boot and to do routine, utility operations, such as reading from and writing to hardware devices and performing basic data manipulation.

EEPROM

On EEPROM (electrically erasable programmable ROM) chips, a higher voltage is applied to one of the pins to erase its previous memory before the new instruction set or data is electronically written.

Flash Memory

Flash memory acts more like secondary storage than like other types of memory because it does not lose its data when the power is turned off. Flash memory is different from a hard drive in that a hard drive holds its data as a magnetized area on a platter, whereas flash memory holds its data electronically. Also, flash memory provides much faster data access than a hard drive does, because a hard drive is a mechanical device and flash memory is an electronic device. Flash RAM is used in notebook computers and digital cameras and is often found on PCMCIA (PC) cards.

Flash ROM

Flash ROM can be used on systemboards, and it allows upgraded versions of the BIOS to be written to it without having to physically replace the chip. Technically speaking, Flash ROM is called EEPROM (electronically erasable programmable read-only memory), which means you can change the programming on the chip through software on your PC.

The updated programming will be retained, even when you turn off your PC for long periods of time, until you change it again.

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