Intel’s “PROM knights” were the engineers who turned a memory reliability problem into a reusable chip, then steadily made that chip easier to use. Dov Frohman developed the EPROM concept behind the 1702; George Perlegos and colleagues advanced the line through the 2708 and 2716 to the electrically erasable 2816. Their work replaced one-time programming with practical ways to revise firmware during development.
What were Intel’s PROM knights?
“PROM knights” is a nickname for the Intel engineers associated with successive improvements to programmable read-only memory. The key figures were Dov Frohman, who devised the EPROM concept, and George Perlegos, who helped develop later EPROMs and the electrically erasable 2816. Phil Salisbury also worked with Perlegos on the 2708 and later joined him in forming Seeq.
The story began with a defect. In 1969–1970, Intel asked Frohman to investigate reliability problems in its 1101 memory. He recognized that charge trapped in silicon dioxide, which had caused trouble, could instead be made into a controllable way to store data. Intel recounts that Frohman demonstrated the concept at the International Solid-State Circuits Conference in February 1971. Gordon Moore later recalled the audience applauding as ultraviolet light erased the stored bits: “The bits fell, and when the final one disappeared, the entire audience broke into applause.” Intel’s account of the demonstration describes the moment.
Who invented EPROM?
Dov Frohman is credited with inventing the EPROM concept. His insight transformed trapped charge from a reliability problem into a means of storing information that could be erased and programmed again. Intel announced the 1702 in 1971, and it sold commercially in 1972. The device gave engineers a way to revise a program without ordering a new mask ROM for every change.
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That mattered especially as microprocessors emerged. Firmware could be changed during development rather than fixed early in a mask ROM. Intel’s historical account describes the resulting reduction in prototype design time as “days or weeks to hours.” Intel’s history of the 4004 era puts EPROM’s practical effect in that context.
How did the Intel 1702 work?
The 1702 stored 2,048 bits, or 256 bytes. It was an erasable PROM with a quartz window over the chip. A programmer wrote data into the device; to erase it, ultraviolet light passed through the window and cleared the stored charge across the chip. After erasure, the device could be programmed again. The window was functional, not decorative: it let UV light reach the memory cells. The Computer History Museum’s chronology records the 1702 as a 1971 user-erasable PROM.
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The erase step made reuse possible but was not instantaneous. George Rostky’s 2002 historical account says erasure could take about half an hour, depending on UV intensity. The 1702 also had substantial voltage and speed limitations. Those constraints help explain why the product line evolved quickly. Rostky’s account in EE Times traces both the early device’s limits and the engineering work that followed.
How did Intel’s EPROM family improve?
| Device | Milestone | What changed |
|---|---|---|
| 1702 | Announced 1971; commercially sold 1972 | 2,048-bit UV-erasable PROM, with a quartz window for bulk erasure. |
| 2708 | Developed in 1974–1975 | 8-kbit n-channel EPROM, developed by George Perlegos and Phil Salisbury for better fit with Intel 8080-era systems. |
| 2716 | 1976 | 16-kbit EPROM; the Computer History Museum identifies it as the first 5-volt-only EPROM, simplifying power requirements. |
| 2816 | Developed in 1978 | Electrically erasable PROM, or EEPROM: electrical erase and byte- or row-level rewriting without a UV lamp or quartz window. |
The 2708 moved the family to n-channel operation and increased capacity. The 2716’s 5-volt-only operation reduced the power-supply complexity associated with earlier parts. The 2816 changed the workflow more fundamentally: electrical tunneling enabled erasure and rewriting without removing a device for UV exposure. The Computer History Museum’s semiconductor chronology identifies the 2716 milestone, while EE Times’ history recounts the development of the 2708 and 2816.
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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteWhat is the difference between PROM, EPROM, and EEPROM?
The names describe different ways to program and erase a memory. PROM is conventionally one-time programmable: programming permanently changes internal links, commonly by blowing fuses. EPROM stores data in a form that can be erased with UV light, typically as a whole device. EEPROM uses electrical erasure, allowing smaller portions to be rewritten.
| Type | Erase method | Package and workflow | Rewrite scope |
|---|---|---|---|
| PROM | Fuse programming; not erasable for reuse | No UV window is needed; program externally before use. | One-time programming. |
| EPROM | Ultraviolet light | Typically has a quartz window; erase with UV, then program again using suitable external equipment. | Bulk erase, then reprogram. |
| EEPROM | Electrical | No UV window or UV eraser; electrical erase and programming may be done in-system on devices designed to support it. | Byte- or row-level rewriting in the 2816 account. |
Exact programming and operating voltages, erase times, speeds, and in-system capabilities vary by device. The historical accounts cited here do not provide a full comparable specification set for all three categories, so a specific chip’s datasheet should govern wiring and programming. In particular, do not assume that every EEPROM supports in-system programming or that an EPROM can be erased while installed.
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What programmer or UV eraser do I need for an old EPROM?
For a UV-erasable EPROM such as the 1702, restoration generally calls for two compatible pieces of equipment: a programmer that explicitly supports the device, and a UV EPROM eraser. The programmer writes the data; the eraser clears the chip through its quartz window. EEPROMs such as the 2816 do not need UV erasure.
- Identify the exact part number. Read the device marking and consult its datasheet. Similar-looking EPROMs can differ in pinout, programming algorithm, voltage requirements, and capacity.
- Check programmer support before connecting the chip. Confirm the exact device number, socket or adapter, pinout, programming voltages, and required supply rails in the programmer’s documentation. “EPROM compatible” alone is not enough.
- Use a UV eraser only for a UV-erasable device. The chip needs suitable ultraviolet exposure through an intact quartz window. Follow the eraser and chip documentation, including safety precautions; do not substitute ordinary room lighting for a specified UV erase process.
- Program and verify the data. Use the programmer’s device-specific procedure and verify the written contents before reinstalling the part. Preserve an image of the original contents first if the chip still holds useful firmware.
Older parts can have unusual voltage requirements, so a modern programmer’s general compatibility claim is not a substitute for checking its supported-device list and specifications. No single programmer model is established here as suitable for every Intel EPROM.
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What followed the 2816?
Perlegos, Salisbury, and Gordon Campbell left Intel to form Seeq in 1981. Their work contributed to the development of in-system EEPROM and later flash-memory directions. The progression from 1702 to 2816 captures the larger engineering shift: first make memory reusable, then make rewriting less disruptive to the system and the people developing it.
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