All PCs need several types of memory in order to work together. We have storage memory, but we also have RAM and ROM , two types of memory that are sometimes confused and, for this reason, today we are going to tell you about their differences , their types and what each of them is used for. they.
Surely you are already clear about what RAM is, since it is one of the components we usually talk about when it comes to PC hardware, and it can be purchased at any computer store. However, although you may not know it, computers also have ROM memory, and it is essential for its operation. We are going to see what each of these types of memory is and what it is for to know their differences.
RAM memory
RAM memory is called by the acronym in English Random Access Memory , or random access memory. Its name is this precisely because its content changes constantly depending on what the PC needs at all times – and it is managed by the processor. It is used to store the programs and data that are being used at all times, so that the processor has access to them immediately, in real time in fact.
This type of memory is volatile , which means that any information stored in it disappears when we turn off the PC. That is why a secondary memory is necessary to store the programs that the PC is going to execute. This memory would be secondary to the contrary that RAM is not used to execute programs, since it is not fast enough.
RAM memory types
Among the existing types of RAM, currently we can find two types:
- DRAM : stands for Dynamic RAM, and it is the most used in PCs and, in fact, in almost any device including smartphones. This type of memory is made up of capacitors that require the controller to store the data stored in it several times per second so that it is not lost. It is used for conventional RAM memories and unlike SRAM it needs to be refreshed every so often to keep the data.
- SRAM : stands for Static RAM, and as the name suggests it is static. In this case the data is stored until the power supply is cut without the controller having to constantly refresh the data; it is faster and uses less power than DRAM, but is used less because it is more expensive to manufacture and allows for much lower densities (capacities). SRAM is used for caches and registers for both CPUs and GPUs.
On the other hand, it should be clarified that NVRAM, Non Volatile RAM, refers to NAND Flash memory, specifically DIMM memory modules that integrate NAND Flash memory chips instead of conventional RAM. Whatever the type of flash memory, it is not used as RAM, except in components that operate at very low clock speeds.
ROM memory
ROM memory is called by the acronym in English Read Only Memory , or read-only memory. The biggest difference between RAM and ROM is that ROM is non-volatile , that is, the stored information is retained even if we turn off the PC. This type of memory has a much lower capacity than RAM and is also much slower.
In the first computers, because the storage memory that was used was very slow, since magnetic disks or tapes were used, it used to include a ROM where the operating system and its BIOS were loaded.
The ROM memory stopped being used as soon as the speed exceeded it and the latency from using it went too high. When that phenomenon happened was when hard drives began to standardize on PCs.
Read-only memory types
Initially, ROM was read-only only, but for a long time it has been simply non-volatile memory that can also be written to… in a few specific ways. In the ROM memory is stored, for example, the BIOS (which as you know can be updated), as well as the firmware of the devices. These are the main types of ROM that are used today:
- Mask ROM : this type of memory is used during the manufacturing process of the devices, and once the data is written, it cannot be modified.
- PROM : means «Programmable ROM», and as its name indicates, the data it stores can be programmed (unlike the Mask ROM, after the manufacturing process). It has the peculiarity that once it is written to it, this data can no longer be modified.
- EPROM : stands for “Electrically Programmable ROM”, and is similar to PROM but allows data to be erased under specific conditions (essentially by exposing it to high intensity UV light).
- EEPROM : stands for “Electrically Erasable Programmable ROM”, and is the most widely used type of ROM memory because it allows data to be erased and rewritten an unlimited number of times.
As a curiosity, many of the fixed function chips that were used in old hardware were built with ROM memories, these chips, starting from specific input data, always end up executing the same “program”, which is encoded in the ROM. But this encoding is not binary as in a conventional RAM or ROM memory. What is sought is the bits when passing through the different transistors of the ROM are manipulated in a certain way to get a specific type of result.
In short, what differences are there?
In essence, RAM is a type of temporary storage, which basically stores the data that the processor must access immediately so that it does not have to be looking for it in the system storage, or calculations that the processor has done. processor and that you need to use them later, so you don’t have to recalculate them.
What differentiates RAM from ROM is not only because it is a fixed memory (that is, it is not volatile but the data remains there even even without power), but it is also read-only and cannot be re-used. write anything on it. This type of memory stores things like BIOS or device firmware.
