PROM, stands for Programmable Read-Only Memory, is a type of memory chip that can be programmed with software to produce different outputs. There are two types of PROMs, namely EPROM and EEPROM. An EPROM has an ultraviolet light-sensitive window so the programming data on it can be erased by exposure to UV rays. The EEPROM, on the other hand, does not show any degradation in its performance even after 100000 cycles of rewriting operations.
The PROM is used as a type of read-only memory in many systems. It can be programmed with software to produce different outputs, which means it has an application not just at the hardware level but also in providing instructions for software programs or data processing. The more common use of this technology today is its role as an operating system’s startup code and BIOS password checker on personal computers.
In some cases, you need to update the programming information stored within a PROM; for instance, when updating your computer’s motherboard or firmware from one version to another. You may then want to re-program all memories containing previous versions so that they contain only up-to-date data instead, including those within the PROM.
Some memory devices, such as a flash drive or hard disk, do not need to be re-programmed but are instead updated with new data by transferring it from another device without deleting any of the old content first. In this case, an update would overwrite previous information stored on your computer’s booting device and replace it with something newer; you may have seen this happen when updating software or starting up for instance Windows updates that install automatically in some cases.
If there is no other way to upgrade your BIOS firmware version (e.g., if you don’t have access to the chip’s programming), then often a technician will use external hardware tools like an SPI programmer connected via JTAG cable to the chip to make changes.