ROM: PROM, EPROM, EEPROM : CISSP Domain – Asset Security
Ahh the various types of ROM. So much fun, right? Okay here goes . . .
ROM stands for read only memory. It’s where the BIOS lives. It’s a non volatile chip: In other words, when you reboot your computer it will still be there.
There are three kinds of ROM:
PROM – Programmable Read Only Memory: is the granddaddy of them all. It can only be written too once.
EPROM – Electronically Programmable Read Only Memory: With the use of ultraviolet light you can write to multiple times. This is where the word “flashing” comes from.
EEPROM – Electronically Erasable Programmable Read Only Memory: This is the modern ROM. It can be erased. It can be updated and doesn’t need to be removed to do so. The most famous kind of EEPROM is a flash memory USB drive. With this type of ROM you can only write to it one bit at a time.