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Difference between PROM and EPROM

These two data storage methods were utilized before for SD cards and hard disk drives. However, there are some main differences between these data storages. A written type of ROM is called PROM, and the user writes this memory only once, and it is electrically programmed at that time. EPROM is a form of ROM that may be read and written. EPROM storage durability is lower than PROM storage permanence because it is more vulnerable to electrical noise and radiation.

In this article, you will learn about the difference between PROM and EPROM. But before discussing the differences, you must know about PROM and EPROM.

What is PROM?

The term PROM stands for Programmable Read-Only Memory. PROM was designed to fulfil the need for a collection of ROMs that may hold a specific memory content. The PROM memory is only written once and is electronically configured by the user either during or after the original chip manufacture. The user supplies the necessary content file and then inserts it into the machine known as the ROM programmer.

The PROM is built using bipolar transistors, which need much power but work very quickly. It has excellent storing stability, which means that the bits don't change until the PROM is reconnected to the programmer and additional fuses are blown. PROM is beneficial when created on a large scale and offers convenience and flexibility.

Advantages and Disadvantages of PROM

There are various advantages and disadvantages of PROM. Some main advantages and disadvantages of PROM are as follows:


  1. Many programming tools are available on the market today, so you don't have to rely on hardwiring the ROM chip to program.


  1. If an error has occurred, PROM data may not be edited or rewritten.

What is EPROM?

EPROM stands for Erasable Programmable Read Only Memory, which is read and written optically (electrically). In order to write an EPROM, the storage cells must stay in their initial state. Therefore, the packed chip is exposed to ultraviolet radiation to remove the storage cells before performing the write operation.

The erasure technique is repeated many times, and a one-time erasure might take up to 20 minutes. EPROM has less storage durability than PROM because it is susceptible to electrical noise and radiation. The EPROM may be reprogrammed up to 1,000 times before it loses reliability. It has a quartz window that surpasses UV light.

The MOS transistor is a programmable element used in EPROM. A floating gate surrounded by an insulator makes up the transistor. The EPROM channel produces negative charges between the drain and source and keeps logic 1. The negative charges shift out from the channel due to the high voltage at the gate, and then these charges are caught in the floating gate and kept logic 0. When the floating gate surface is exposed to UV light, the negative charges from the floating gate are transferred back to the channel and restored logic 1. This phenomenon is referred to as hot electron injection.

Advantages and Disadvantages of EPROM

There are various advantages and disadvantages of EPROM. Some main advantages and disadvantages of EPROM are as follows:


  1. EPROM has the ability to remove and rewrite programs.
  2. EPROM is less expensive than PROM.
  3. EPROM is a non-volatile memory.


  1. EPROM is not able to erase any specific bytes; if you remove one byte, the entire EPROM is removed at once.
  2. EPROM uses a lot of static power.
  3. The EPROM Memory Chip's data deletion requires more time.

Main Differences between the PROM and EPROM

Difference between PROM and EPROM

Here, you will learn the main differences between PROM and EPROM. Some main differences between PROM and EPROM are as follows:

  1. The PROM chip is only programmed once. In contrast, the EPROM chip is reprogrammable.
  2. The EPROM is more expensive than the PROM in terms of price.
  3. Electric noise and radiation do not affect PROM storage permanence, while these factors may impact EPROM storage stability. Moreover, the EPROM storage may store the information or data for 10 years.
  4. PROM is entirely wrapped in a plastic cover. On the other hand, the EPROM is protected by a transparent quartz pane that allows UV rays to pass through.
  5. The PROM has persistent memory, so the process is irreversible. On the other hand, EPROM memory is not permanent, so that you can reverse the storage process.
  6. PROM is more flexible and scalable. On the other hand, EPROM is less scalable and adaptable.
  7. PROM has long storage endurance. On the other side, EPROM has shorter storage endurance than PROM.
  8. PROM is a form of ROM that may only be written. On the other hand, EPROM is a form of ROM that may be read and written optically.

Head-to-head comparison between the PROM and EPROM

Here, you will learn the head-to-head comparisons between the PROM and the EPROM. The main differences between the PROM and the EPROM are as follows:

Full Form It stands for Programmable Read-Only Memory. It stands for Erasable Programmable Read-Only Memory.
Basic It is a one-time programmable only. It is programmable.
Cost Efficiency It is more cost-efficient than EPROM. It is less cost-effective compared to PROM.
Storage Endurance It has large storage endurance. It has lower storage endurance.
Version It is an older EPROM version. EPROM is an improved and newer version of PROM.
Type PROM is a read-only type of memory storage system. It may be both a read and write memory storage system.
Scalability It is very versatile and scalable. It isn't as flexible or scalable.
Preservation It is encased in plastic cowls. It requires being stored in rock crystal windows because UV radiation would transfer via it.
Transistors Bipolar transistors are used in the PROM. The MOS transistors are used in EPROM.
Effect of Miscalculation It will become useless if there is a flaw, mistake, or calculation error while writing to PROM. Since an EPROM is re-writable and erasable, we can utilize it several times, even if we make a mistake when writing on it.


In summary, the PROM is less expensive than the EPROM, but it can only be programmed once, whereas the EPROM can be programmed several times, but the chip must be taken out of the system to remove the data.

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