From EPROM to EEPROM: How Firmware Memory Evolved in Operating Systems and Modern PCs

1. Introduction

In the early days of computing, non-volatile memory was essential for bootstrapping a system. Among the earliest technologies used for this purpose were EPROMs (Erasable Programmable Read-Only Memory), which allowed firmware like BIOS to be stored in a non-volatile yet modifiable format. As computing evolved, so did memory technologies, leading to the widespread adoption of EEPROMs (Electrically Erasable Programmable Read-Only Memory) and flash memory in modern personal computers and embedded systems. This article explores the critical role EPROMs played in early operating systems and how their legacy has transformed with modern EEPROM technologies.

2. What is an EPROM?

EPROMs were a significant breakthrough in the 1970s and 1980s, providing a non-volatile memory medium that could be programmed with a high voltage and erased with ultraviolet light. These chips were used to store firmware-permanent software responsible for initializing hardware and launching the operating system.

The ability to program and reprogram EPROMs made them far more flexible than mask ROMs, which were fixed at the factory. Developers could test and update firmware during the prototyping and development phases…