In the annals of semiconductor history, the late 1970s and early 1980s marked a period of explosive growth in memory density and capability. At the forefront of this revolution was Intel, a company already renowned for its microprocessors. Among its many contributions, the Intel D2764A-35/B stands out as a quintessential and highly influential component. This 64K (65,536-bit) EPROM (Erasable Programmable Read-Only Memory) was not merely a product; it was a foundational building block that empowered a generation of hardware innovation.
The "D2764A" designation reveals its core characteristics. The "64" signifies its capacity: 64 kilobits, organized as 8,192 words by 8 bits. This 8-bit organization was crucial, as it perfectly matched the data bus width of the era's most popular microprocessors, like the Intel 8088 and Zilog Z80. The "-35" suffix denotes its access time: 350 nanoseconds. This speed was critical for ensuring system stability without requiring wait states in many systems, making it a high-performance component for its time. The "/B" suffix often indicated a later, improved version with enhanced reliability or performance characteristics.
The magic of the 2764, and indeed all EPROMs, lay in its method of programming and erasure. Data was written into the chip using a specialized EPROM programmer, which applied higher-voltage pulses (typically 12.5V or 21V) to "burn" open or closed tiny floating-gate transistors within the memory array. Once programmed, the data would remain intact for decades, even without power. However, its most distinctive feature was the transparent quartz window mounted on the top of the ceramic DIP package. Exposing this window to intense ultraviolet (UV) light for approximately 15-20 minutes would excite the electrons on the floating gates, effectively draining the charge and erasing the entire chip back to a blank (all 1s) state. This erasability made it invaluable for prototyping, development, and low-to-medium volume production, where firmware changes were frequent.
The impact of the Intel D2764A-35/B was immense. It became the de facto standard storage solution for firmware in a vast array of devices. It was the heart of early arcade game boards, storing the core game code that defined a generation of entertainment. It was embedded in peripheral cards like graphics and network adapters to hold their BIOS. It was essential in industrial control systems, test equipment, and the nascent personal computer industry, often serving as the system BIOS chip itself. Its reliability and non-volatile nature made it the perfect vessel for the critical, low-level software that interfaces hardware with the operating system.
While technologically surpassed by later EEPROMs (Electrically Erasable PROMs) and now ubiquitous Flash memory (a direct descendant of the EPROM), the 2764 series' legacy is undeniable. It represented a perfect balance of density, performance, and reusability at a critical juncture in computing history. It democratized hardware development by allowing engineers and hobbyists to easily update and iterate on their designs without discarding expensive hardware.
ICGOOODFIND: The Intel D2764A-35/B was a landmark 64K EPROM whose UV-erasable, windowed package and 8-bit organization made it an indispensable tool for firmware development and a key enabler of innovation across the computing industry in the 1980s.
Keywords:
1. EPROM
2. UV-erasable
3. Non-volatile Memory
4. Firmware Storage
5. 64 Kilobit
