Read-only ROM What is it and what is it for? How does it work and what types are there?

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Craig Zacker
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When we talk about read-only ROMs, we are referring to the type of memory used in cell phones, in computers and other electronic devices. It is important to understand the difference between RAM and ROM and what types exist.

Its key feature is that it only serves to give access only to reading and at no time has access to writing. This means that the information can be recovered, but it cannot be intervened, either they can be modified or modified. Therefore, processes like making Google Chrome consume less RAM are obviously not applicable in this case.

ROM memories only have sequential access and do not depend on a power source, you can turn off the computer and the information will remain inside it. The content that ROM memory has cannot be changed, or at least, cannot be changed daily or easily.

The generation of the ROM memory of one reading comes with information pre-installed by the manufacturer, such as the " Recovery mode »On mobile phones or when viewing and finding the Windows Server Product Key, being clear examples. I invite you to continue reading this wonderful section which contains important information about the ROM.

What is the ROM for?

ROM is read-only has different uses, but it has only two uses which are of major importance, they are the following:

The first is data storage. People who use the PC generally don't have access to the system ROM.


Then it is used to save all unnecessary data that does not require any type of modification in the cycle of a product. Such as logical and mathematical operators, lookup tables and other technical information.

The second is software archiving. Generally, in the 80s, computers had the operating system stored in ROM.

With the purpose of the users could not modify it incorrectly so that the computer stops working. Today it is still used to install basic boot or operating software such as POST, SETUP or BIOS.

This type of read-only ROM performs its function much slower than RAM, so generally the content that the ROM has it usually uses RAM to work better.

The types of memory and how they work

Since the read-only fixed memories came out, the ROM of read only yes è gradually evolved.

So now the memory can be programmed and reprogrammed. The types of existing ROM memories are as follows:


It is a type of programmable memory developed in the 70s by the company called Texas Instrument.

I programmable read-only memory chips have inside them designed to compress a large number of diodes or fuses.

These diodes can perform their function by means of a device called "ROM Programmer", which generates 12 V in the marked memory boxes.

When the fuses are blown, correspond to bits number 0. Gli other bits instead correspond to 1.


It is the first of the solo memories reading that have been created, its function was to write binary information on a small silicone plate through a mask.

Although nowadays this type of procedure is no longer performed in this way, the functioning of ROMs has evolved.


The EPROM memory are memory PROMs that can be deleted. The chips have a small glass panel that allows ultraviolet rays to pass through.

When the panels receive the UV ray in a certain size o wavelength, the fuses are rebuilt. This means that the memory bits have returned to 1.


It is for this reason that EPROM-type memories are known as erasable memories, since PROM memories remain at 0 when they are burned.


The EEPROM memory they are still erasable PROM memories, but they differ from EPROM memories in that they can be erased by electric current.

There is currently a variety of this type of memory, known as flash memory, also as flash EPROM o flash ROM.

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