EEPROM vs EPROM: Key Differences, Pros & Cons Explained
EEPROM is a byte-erasable, electrically rewritable memory chip; EPROM is an older, bulk-erasable chip that needs UV light to wipe data.
Engineers grab “EPROM” when they mean the UV-windowed part from the ’80s, but “EEPROM” slips in because both sound alike and live in the same firmware toolbox. Hobbyists often confuse them when shopping for Arduino upgrades, assuming any “PROM” works the same.
Key Differences
EEPROM lets you rewrite single bytes on the fly using a 5 V signal; EPROM must be popped out, blasted with 20 min of UV, then fully reprogrammed. EEPROM endures ~1 million cycles; EPROM tops out near 1,000. Package tells all: EPROM has a quartz window you can see through.
Which One Should You Choose?
Need frequent updates in-circuit—like firmware patches or IoT settings? Go EEPROM. Tight budget and one-time factory code? EPROM still sells for pennies and stores forever. Modern flash often replaces both, but legacy gear keeps EPROM alive.
Can I convert an EPROM to EEPROM?
No; the silicon layers and erase mechanisms are fundamentally different—swapping chips is the only path.
Why does EPROM have a little window?
That quartz window lets UV photons hit the floating gate, knocking off trapped electrons to reset all bits at once.