Intel E28F008SA-120: A Deep Dive into the 8-Megabit Flash Memory Chip
In the landscape of late 20th-century computing, the evolution of non-volatile storage was pivotal. Among the key enablers of this revolution was Intel's family of flash memory chips, with the Intel E28F008SA-120 standing as a significant contributor. This 8-megabit (1-megabyte) chip encapsulated the cutting-edge technology of its era, providing the reliable, erasable, and rewritable storage necessary to boot countless systems and store critical firmware.
Fabricated using Intel's advanced EPROM-based flash technology, the E28F008SA-120 was designed for a 5-volt single power supply operation, simplifying its integration into a wide array of computing devices. The "-120" suffix denotes a 120ns maximum access time, a critical speed grade that determined how quickly the processor could retrieve data from the chip. This balance of speed and capacity made it ideal for its primary role: storing the BIOS (Basic Input/Output System) for desktop computers and firmware for various peripherals.
A key architectural feature of this chip is its organization. It is configured as 1,048,576 words of 8 bits each (1M x 8), a standard and logical arrangement that aligned perfectly with the 8-bit and 16-bit data buses of contemporary microprocessors. This structure allowed for efficient addressing and data transfer. The chip's package, a 40-pin PDIP (Plastic Dual In-line Package), was the industry workhorse, ensuring easy handling and compatibility with existing socket and board designs.
The "SA" in its part number signifies that this component belongs to Intel's second-generation flash memory family, which introduced several user-friendly improvements over its predecessors. Most notably, it featured a command-driven interface that allowed it to be reprogrammed in-system (in-circuit) without requiring removal from the board or exposure to ultraviolet light—a major drawback of standard EPROMs. This was achieved by writing specific command sequences to the chip's internal register, enabling functions like byte programming, block erasure, and status reading.
The programming and erasure processes were managed by an internal state machine, insulating the host system from complex timing protocols. Engineers could erase the entire chip or predefined blocks of memory and then reprogram it thousands of times, making development and field updates vastly more efficient. Furthermore, the chip incorporated hardware and software data protection features to prevent accidental corruption of the stored code.
In application, the E28F008SA-120 was a cornerstone of reliability. It was the silent foundation upon which systems booted, providing the first code executed by the CPU upon power-up. Its presence was ubiquitous in PCs of the 1990s, networking equipment, industrial control systems, and any embedded application requiring robust and updatable firmware storage.
The Intel E28F008SA-120 was more than just a memory chip; it was a foundational technology that enabled the software-defined hardware revolution. Its combination of a 5V-only operation, a fast 120ns access time, and a sophisticated in-system reprogrammable architecture set a high standard for reliability and convenience in the firmware storage market. It stands as a testament to an era of rapid innovation that laid the groundwork for the modern connected world.
Keywords:
Flash Memory
BIOS
In-System Reprogrammable
Non-Volatile Storage
120ns Access Time
