Difference Between EPROM and EEPROM

We all are aware of ROM i.e. Read-Only Memory which contains the data required to boot up the computer system. It is a non-volatile memory, and it can not be modified easily or even sometimes not at all. But the modern ROM can be erased and reprogrammed in some way. Today we have modified version of ROM that are EPROM (Erasable Read-Only Memory) and EEPROM (Electrically Erasable Read-Only Memory). EPROM and EEPROM can be erased and reprogrammed again but at a very slow speed. Erasing requires special equipment and can be done at a limited number of times.

EPROM and EEPROM both are erasable and can be reprogrammed, but the basic difference between them is that EPROM is erased using Ultra violet rays whereas, EEPROM can be erased using electric signals. Let us discuss the differences between EPROM  and EEPROM with the help of comparison chart shown below.

Content: EPROM Vs EEPROM

1. Comparison Chart
2. Definition
3. Key Differences
4. Similarities
5. Conclusion

Comparison Chart

BASIS FOR COMPARISON	EPROM	EEPROM
Basic	Ultraviolet Light is used to erase the content of EPROM.	EEPROM contents are erased using electronic signal.
Appearance	EPROM has a transparent quartz crystal window at the top.	EEPROM are totally encased in an opaque plastic case.
Erased and Reprogrammed	EPROM chip has to be removed from the computer circuit to erase and reprogram the computer BIOS.	EEPROM chip can be erased and reprogrammed in the computer circuit to erase and reprogram the content of computer BIOS.
Technology	EPROM is an older technology.	EEPROM is a modern version over EPROM.

Definition of EPROM

Though ROM (Read-Only Memory) and PROM (Programmable Read-Only Memory) are inexpensive but changing them over the time adds to cost. To overcome this EPROM  were introduced. EPROM is an Erasable Programable Read-Only Memory.  EPROM was invented by Dov Frohman in the year 1971 at Intel.

EPROM  is a nonvolatile memory that retains data even after the power is switched off.  The EPROM contains the computer BIOS used during the boot up of the computer. It is a read-only memory whose content can be erased by exposing the EPROM chip to ultraviolet light. EPROM can be recognized easily as there is a transparent quartz crystal window lid at the top of this chip.

EPROM is an array of floating gate transistors. Each transistor is programmed individually using an electronic device that supplies the higher voltage than that of normal voltage used in digital circuits. Once programmed, the EPROM  retains its data minimum up to 10 years many of them also retains data up to 35 or more years. The quartz crystal window slits are covered by the adhesive label to avoid the contact of UV light or camera flashes.

EPROM  can be erased a limited number of times. As during each erasure, the silicon dioxide around the gates accumulates the damage which makes the chip unreliable after several thousand erasures.

Definition of EEPROM

EEPROM is an Electrically Erasable Programmable Read-Only Memory. Like EPROM, EEPROM can be erased and reprogram, but the difference lies in how the content in both are erased. Like in EPROM, the content is erased by exposing it to the UV light but, in EEPROM the content is erased by the electrical signals.

George Perlogos invented EEPROM in the year 1978 based on the technology of EPROM. EEPROM is a non-volatile memory that retains its content even if the power is switched off. It stores the small amount of data used for computer BIOS. It was a replacement for the PROM and EPROM.

EPROM allows you to change the BIOS of the computer without removing the EEPROM chip from the computer. EEPROM can be erased in the circuit by applying the special programming signals. EEPROMs are also organized as the array of floating-gate transistors.

Like EPROM, EEPROM has a limited life that is it can be erased and reprogrammed up to some hundred or thousand times, and thus a life of EEPROM becomes an important concern while designing an EEPROM.

Key Differences Between EPROM and EEPROM

1. The key difference between EPROM and EEPROM lies in the method of erasing the content inside them, EPROM’s content is erased by exposing the EPROM chip to the UV lights whereas, the EEPROM’s content is erased by applying the electric signal to the chip.
2. EPROM can be easily recognised by its appearance as it has a transparent quartz crystal window lid at the top of the chip for exposure of  UV light, while EEPROM is totally encased inside an opaque plastic case.
3. To erase and reprogram the EPROM the chip has to be removed and taken out from the computer. On the other hands, EEPROM chip is erased and reprogrammed in the circuit of the computer itself.
4. EPROM was the first reprogrammable ROM whereas, the EEPROM is the replacement and modern version of EPROM.

Similarities:

• Both can be erased and reprogrammed.
• Both have the content of computer BIOS.
• Both has the limited life.

Conclusion:

EPROM  was the replacement for ROM and PROM because as ROM and PROM were cheaper but changing them over the time adds to the cost and the user was not able to change the content of BIOS. So, EPROM was developed to overcome the downside of ROM and PROM. However, EEPROM is the modern version of EPROM