Types of memories of a computer

What is computer memory?

The  memory  is one of the fundamental components for the proper functioning of our PC , since its existence allows the computer to start, the data is processed, the instructions are executed for different programs and others.

On the other hand, the greater the amount of memory that a PC has, the greater the performance  and the improvement in the performance of the computer.


However, a computer works with four different types of memories, which serve to perform various functions. These are  RAM memory, ROM memory, SRAM or Cache memory and Virtual or Swap memory.

Memory types:

RAM memory

The most important is the so-called  RAM (Random Access Memory),  since our computer could not function without its existence.

Different types of information are stored in RAM, from temporary processes such as file modifications, to the instructions that enable the execution of the applications that we have installed on our PC.

For this reason, it  is constantly used by the microprocessor, which accesses it to find or temporarily save information regarding the processes carried out on the computer .

Within the  RAM memories  there are different types of technologies that differ mainly in their access speed and their physical form. Among them we find  DRAM, SDRAM, RDRAM , among others.

The so-called  DRAMs (Dynamyc Random Access Memory)  have been used in computers since the first years of the 80’s, and even today they continue to be used. It is one of the cheapest types of memory , although its greatest disadvantage is related to the speed of the process, since it is one of the slowest, which has led manufacturers to modify their technology to offer a better product.

As for the type of SDRAM technology  , derived from the first, it began to be marketed at the end of the 90’s,  and thanks to this type of memory processes were significantly streamlined , since it can operate at the same speed as the motherboard. to which it is incorporated.

For its part, RDRAM technology   is one of the most expensive due to its manufacturing complexity, and is only used in  large processors, such as Pentim IV and higher.

Another difference between the different  RAM memories  is found in the type of module in question, which can be  SIMM (Single in line Memory Module), DIMM (Double Memory Module) and RIMM (Rambus in line Memory Module),  depending the number of pins it contains and the physical size of the module.

ROM memory

In addition to RAM,  computers work with memory called ROM, Read Only Memory,  which, as its name indicates, is a read-only memory, since most of these memories cannot be modified because they do not allow his writing.

The ROM is built into the motherboard and is used by the PC to start the BIOS , which is basically a program that has the right to guide the computer instructions during boot.


Among its functions, the  BIOS  begins with the process called  POST (Power On Self Test)  during which it will inspect the entire system to verify that all its components are working properly to initiate boot.

To do this, the  BIOS  consults a registry in which all the information regarding the hardware that we have installed in our PC is found, to verify that everything is in order. This register is called CMOS Setup .

Although we mentioned that in many cases the ROM memory cannot be modified,  nowadays a large number of motherboards incorporate new models of ROM that allow it to be written,  so that the user can make changes to the  BIOS  in order to improve its operation.

The fundamental difference between RAM and ROM lies in speed , since ROM  , being a type of sequential memory, needs to go through all the data until it finds the information it is looking for, while RAM works randomly. , which makes you access specific information directly.

This factor makes the speed of the  RAM  noticeably higher. Likewise, its capacity is greater than that of ROM memory  , and unlike the latter, RAM is not integrated into the motherboard, which allows the user to expand the amount of RAM on their PC.


Another type of memory used by computers is called  SRAM , better known as  Cache memory.

Both the processor, the hard disk and the motherboard have their own cache memory,  which basically protects different addresses that are used by the RAM to perform different functions , such as running programs installed on the PC.

The process carried out by the cache  is to save the locations on the disk that the programs that have been executed occupy, so that when they are started again the access to the application will be faster .

There are three different types of cache:

– The  L1 cache  that is inside the processor and works at the same speed as it, and in which instructions and data are stored.

– The  L2 cache  that are usually of two types: internal and external. The first is inside the motherboard, while the second is in the processor but externally, which makes it slower than the L1 cache.

– The  L3 cache  that is only incorporated into some of the most advanced microprocessors, which results in a higher processing speed.

Swap memory

In some computers, especially those that  have Microsoft Windows or Linux operating systems, we will also find the so-called virtual or Swap memory .

This type of memory, which works in a similar way to the cache,  is created by Windows or Linux to be used exclusively by the operating system.  In the case of Linux this so-called  swap memory  is generally located in a different partition of the disk, while in the Microsoft system it is a file within the operating system itself.


On many occasions,  virtual memory tends to produce certain problems that cause the PC to hang , since this type of memory has been created by the system inside the hard disk and can sometimes exceed the processing capacity.

In the execution of programs through virtual memory,  we will only get as a result that our PC becomes slower,  since it reduces the processing speed of the hard disk.

The best way to avoid this problem  is to expand the amount of RAM on our PC , so that the system does not need the creation of extra virtual memory, and therefore slows down the processes during our work.

RAM memory types

DDR memories

According to the type of motherboard that we use in our PC ,  it will be provided with different types of sockets according to its age , and it may use  DDR, DDR2, DDR3 or DDR4 RAM .

The acronym DDR  is used to abbreviate the concept “Double Data Rate” , whose definition is double transfer rate memory, and it is a series of modules that are composed of synchronous memories, called SDRAM,  and although they have the same size Of the SDRAM DIMMs , the DDR-SDRAM  have more connectors , since while the normal SDRAM has 168 pins, the DDR-SDRAM has 184.

DDR memory

DDR memories work by transferring data through two different channels , simultaneously and in the same clock cycle with a transfer of a volume of information of 8 bytes in each clock cycle. However, they are compatible with more powerful processors in terms of clock cycles.

With regard to DDR2 memory,  it is basically the second generation of DDR SDRAM , which has managed to improve certain aspects by providing faster simultaneous processes.

Being a more modern technology,  DDR2 has notable differences with its predecessors , among which the most significant has to do with the minimum transfer value, since while  in traditional DDR it is 1600Mbps, in DDR2 it is doubled to 3200Mbps.

DDR2 memory

This allows a greater bandwidth in the processes, since  DDR2 memories have higher latency because they work with 4 bits per cycle (2 going and 2 return) within the same cycle and under the same frequency of a conventional DDR .

Unfortunately, DDR and DDR2 are not compatible, so if you have a PC whose motherboard has sockets for DDR, you will not be able to use DDR2 memories , since the latter have 240 pins, which allows reducing its voltage to 1.8V, while DDRs use a voltage of 2.5V .

The  voltage reduction in the second generation of DDR memories have incorporated a great improvement , because in this way the energy consumption and therefore the heat generation are considerably reduced.

The advance in the development of the technology of this type of RAM memory produced  the DDR3 modules , whose most important manufacturer so far has been the company Samsung Electronics.

DDR3 incorporates important improvements in the field of DDR SDRAM memories , among which stands out the fact that it can  transfer data at an effective clock rate of 800-1600 Mhz , greatly surpassing previous DDRs, since DDR2 they have a rate of 533-800 MHz and the DDR of 200-400 MHz.

DDR3 memory

This allows a greater bandwidth in the processes, significantly noticeable in the operation of the PC , in addition to having doubled its latency to 8 bits, in order to increase its performance, and  double its minimum transfer rate to 6400Mbps, in comparison to DDR2 that have a rate of 3200Mbps .

DDR3s consume only 1.5V , thanks to the implementation of 80-nanometer manufacturing technology. This change reduces energy consumption and heat generation , thus increasing the speed of the processes.

Regarding the physical aspect,  although the DDR3 have 240 pins, that is to say the same number as the DDR2, both types of memory are incompatible , since the pins have been located differently.

DDR4 memory

DDR4 memories have a speed of 2,667 Mhz and its transfer rate is 21,300 Mbps.

GDDR memories

In the market, in addition to the typical DDR type RAM, we can also find a variant of it, called GDDR SDRAM (Graphics Double Data Rate Synchronous Dynamic RAM), which is a type of memory that was specifically designed with the Purpose to be used in the field of video rendering, usually working as a team with the GPU of our graphics card.

With this type of memory, we will be able to create very complex 3D graphic structures, for which we need a large amount of memory. However, with GDDR memories, which are much faster, the amount of memory required for these processes is reduced, which means less money and space, although the price of GDDR memories does not allow them to be used by the average user. on a tight budget in your home deployments, as they are much more expensive to produce than DDRs, which translates to a much higher price.

Although GDDR-type memories share many of the technical characteristics with DDR-type memories, the truth is that they are not completely the same. In this sense, GDDR memories, being optimized for use in video rendering, prioritize bandwidth, not latency. GDDR memories also work in compliance with the DDR standard specified by the JEDEC, which is why it is capable of sending two bits or 4 for each clock cycle, although in this case GDDR memory is optimized to achieve higher frequencies and a bus width. larger, allowing you to minimize access time to instructions stored in memory.

GDDR memories, like DDRs, have evolved over time, which is why we can find multiple variants. From this point on we will know the different types of GDDR memories on the market.

GDDR: The first type of GDDR on the market. Its effective working frequency was between 166 and 950 MHz with a latency of 4 to 6 ns.

GDDR2: In this type, the operating frequency was improved, which ranged from 533 to 1000 MHz, and could offer a bandwidth of between 8.5 to 16 GB / s.

GDDR3: Especially used by some models of ATI and Nvidia graphics cards, these memories can operate between 166 and 800 MHz.

GDDR4: Quickly replaced by GDDR5, they were only used by some AMD models.

GDDR5: One of the most widespread GDDR memory types in recent years. It is used in mid-range and high-end video cards from manufacturers such as Nvidia, AMD and Radeon, among others. These memories are capable of offering a bus width close to 20 GB / s in 32-bit buses and 160 GB / s in 256-bit buses, the operating frequency can reach up to 8 Gbps. It should be noted that this type of memory is also installed in game consoles such as the Xbox One and the PS4.

GDDR5X: This memory is basically an evolution of the GDDR5 technology that is used in some models of video cards. They offer an operating frequency of 11 Gbps and a bandwidth of 484 GB / s over a 352 bit bus.

GDDR6: At the moment, this is the latest version of GDDR memory available. They are capable of offering up to an operating frequency of 14 Gbps with a bandwidth of 672 GB / s over a 384 bit bus. This type of memory is used in high-end video cards such as the Nvidia Titan RX.

Annex 1: ROM memory

ROM memory is perhaps the most important hardware element of computers and portable devices such  as cell phones, smartphones and tablets, among many others, since in  this small electronic component all the necessary information is stored so that the device starts up  and can comply with its function.

The term ROM is an abbreviation of the Saxon term  “Read Only Memory”  which in Spanish means “Read Only Memory” , and as its name indicates, this type of memory stores information that can only be accessed, that is, it cannot be written with new data,  except through special procedures such as when we are updating a BIOS.

ROM memory

What is ROM memory?

Basically,  a ROM memory is a chip that inside stores the necessary information to be able to start an electronic device such  as a computer or a smartphone, and whose main characteristic is to  have the ability to preserve the data it contains even when there is no power that powers it,  unlike RAM memories, which if not energized, immediately lose their content.

The term ROM nowadays is used by convention, and they  basically come from when ROM memories were developed and left the factory with the data stored  in them, and there was no way to write them.

ROM memory

Nowadays it is possible to find  memories that fulfill the same function of the old ROMs but that can be written, called EPROM and Flash EEPROM,  however writing in this type of memory is a complicated task and that cannot be done directly, except with special tools and procedures, which most of the time are not available to the average user.

These EPROM and Flash EEPROM memories can be written many times, which favors, for example, that  updating the BIOS of a computer can be a frequent task and that does not present problems. Such is the adoption of this type of memory to fulfill the role of ROM that we will practically not be able to find on the market  devices that contain ROM of the oldest type  since the end of the first decade of the 21st century.

What is ROM for?

ROM memories in devices fulfill the important function of  storing inside them the code that is needed to start the different modules that make up a computer,  that is, everything that is required to start working with it. Likewise,  the ROM memory fulfills the function of starting the operating system of the PC  on which it is installed.

In addition to being used for managing the PC boot process,  ROM is used for the initial system check  and various input and output device control routines.

ROM memory

The capacity offered by the ROM memory to be able to preserve data even if it is not energized, makes it ideal for the work of starting a computer,  since the data stored in the ROM memory does not alternate or degrade in the absence of electricity to feed it ,  that is, they are always the same,  so the device they manage will always behave in the same way.

ROM memory types

Over the years, ROM memories have evolved to adapt to new technologies. Currently,  there are three basic types of ROM memory.

ROM (Read Only Memory)

This type of ROM or “Read Only Memory” was the first to be developed and manufactured,  and the information that had to be stored in it was recorded using a procedure that involved the use of a silicone plate and a mask . This type of ROM memories are no longer used, being replaced by the memories detailed below.
ROM memory

PROM (Programmable Read Only Memory)

The PROM memories, also known as “Programmable Read Only Memory”, saw the light at the end of the 70s, and their programming, that is to say, the loading of the data that they had to contain,  was carried out by burning certain electronic components, called diodes, with a voltage overload using a device known as a “ROM Programmer”.  The diodes affected with the load correspond to “0”, while the others correspond to “1”.

ROM memory

EPROM (Erasable Programmable Read Only Memory)

EPROM type memories, also known as “Programmable and Erasable Read Only Memory”, are basically PROM type memories but they have the particularity of being able to be erased. The way to program these memories is through rays of ultraviolet light that penetrate the circuit through a window in the encapsulation of the chip.  As soon as the chip is exposed to UV light, all bits return to their “1” state.

ROM memory

EEPROM (Electrically Erasable Programmable Read Only Memory)

The EEPROM memories also known by the name “Electrically Erasable Programmable Read-Only Memory”, are, like the PROM memories, erasable,  however this procedure in the EEPROM memories is simpler , since it can be carried out by means of a certain current electrical.

It should be noted that EEPROM memories offer a variant called  Flash EEPROM,  which uses fewer components, specifically a single transistor, instead of the 2 or 3 that EPROM memory uses. It also offers the ability to read record by record,  instead of a full page reading like EEPROM memory.

ROM memory

Differences between RAM and ROM memories

As we know, there are two types of memory in a computer, ROM and RAM, and each of them fulfills a very different function. RAM memory, or random access memory,  is that memory accessed by the operating system to search for the data that both the user and the operating system are using,  since it is a much faster method than searching for it on the hard disk.

RAM memory can be read and written multiple times,  however RAM is temporary,  since the data it contains is erased immediately in the absence of power, that is, when it loses power.

ROM memory

In contrast,  ROM memory is not affected by power supply,  which makes this type of memory the ideal medium for storing the data necessary for a device to function. In addition, the condition of not being writable, at least by the usual means available to the average user,  guarantees that it will keep the data it contains in any situation , so the device will always turn on and follow the same routine.

Annex 2: Cache memory

Cache memory was  born when it was discovered that the memories were no longer capable of keeping up with the speed of the processor,  causing the latter many times to stay “waiting” for the data that the RAM  memory had to deliver in order to complete its tasks, losing a lot performance.
If at the time of 386, year 1991, the speed of the memories was already a limiting factor, imagine this problem today, with the processors we have today.


To solve this problem, they began to use cache memory,  an ultra-fast type of memory that serves to store the data that is most frequently used by the processor,  avoiding, most of the time, having to resort to the comparatively slow RAM.

Without the cache memory, the performance of the system would be limited to the speed of the memory, which  could drop up to 95% !

The types of cache memory

Two types of cache memory are used, called primary cache, or  L1 cache  (level 1), and secondary cache, or  L2 cache  (level 2). The primary cache memory is embedded in the processor itself and is fast enough to keep up with speed. Whenever a new processor is developed, a faster type of cache memory must also be developed to accompany it. As this type of memory is extremely expensive (it is hundreds of times more expensive than conventional RAM memory) only a small amount of it is used. To complement this, a slightly slower type of cache memory is also used , which is called secondary cache, which, because it is much cheaper, allows you to use a greater quantity. 

How to install cache memory?

First, you must make sure that the  motherboard  allows the installation of cache memory. The motherboards that allow installation have a socket called COAST where the cache memory module is placed . Generally, you need to change the cache size configuration jumpers. The correct position of the jumpers must be consulted in the manual of the plate. If after this configuration the PC does not turn on, it means that the cache memory module is faulty or is incompatible with the motherboard. In this case, the module must be changed. When everything is working, the memory cache should be enabled in the PC BIOS.

Check the existence of cache memory on the PC?

There are several programs for this purpose. One of them is called PC-Config , it is shareware and can be downloaded for free on the internet. In addition to testing the cache, this program does not provide important information about the PC , such as the type of memory installed and the type of  chipset .

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