Computer RAM Explained

Computer RAM explained

The RAM (Random Access Memory) works as a working memory for computer programs, files and for everything else used by the user. Once the program and the data it needs is in the RAM, the program will work faster. Without RAM the programs and files would have to be always read from the storage drives, this would make using computers very slow. RAM is a volatile memory which means that it is emptied every time the computer restarts.

The data needed is loaded into the RAM, which then inputs the data to the processor. The speed of the RAM is advertised in MHz (Megahertz). The higher the MHz is, the faster the RAM can work. However, there are other things you need to know when you are buying the correct RAM for your system. In this post, I cover everything you need to know about RAM so that you can get the best possible RAM that will work in your system.

RAM Types

There are a number of different types of RAM. Two types that are usually confused are SRAM and DRAM. SRAM means Static Random Access Memory and it is used as the cache of the CPU. CPU’s cache is located inside the CPU, you don’t need to worry about it when selecting RAM memory for your PC.

DRAM means Dynamic Random Access Memory and it is cheaper to manufacture than SRAM. DRAM can be divided into many different types as well, one of the DRAM types is used in the memory sticks that are plugged into the motherboard. That is the type of memory we are interested in this post.

The memory sticks are SDRAM (Synchronous Dynamic Random Access Memory). SDRAM is pretty much obsolete nowadays since the DDR memory type displaced it.


SDRAM DDR memory is divided into different versions. DDR memory is the type of SDRAM used in the memory sticks and it is often referred as a RAM when speaking about computers work memory.

DDR means Double Data Rate Synchronous Dynamic Random Access Memory. It doubles the data transfer speeds compared to SDRAM, as the name tells us. DDR has been developed further and it can be divided into different versions. The DDR versions are marked with a number, but nowadays DDR and DDR2 SDRAM is pretty hard to find from anywhere since it hasn’t been in use for many years.

DDR3 started to appear in 2007 but is still commonly used. The newest version, DDR4 started appearing in 2014 and it is faster than DDR3. However, not all processors and motherboards can support DDR4 memory. Be careful with RAM purchases when you are upgrading your older system. When it comes to building a new system, it is fairly simple to just get the newest gear (that are compatible) and match it with the DDR4 memory sticks.

DDR slots are called as DIMM slots, it means Dual In-line Memory Module. RAM sticks are also called as modules. Most motherboards have four DIMM slots. All DDR memory modules have a notch on the pins that connect in the slot. However, in every DDR version, the notch is in a different place so that you can’t install wrong DDR version in the slots.

DIMM slots with four RAM modules

DIMM slots with four RAM modules.


Dual-Channel Memory

Memory modules are supposed to be added in as pairs. This is because the modern motherboards have a dual-channel chip in them, which allows the used memory to communicate with two channels. The more communication channels, the faster the memory is able to do its work.

DDR memory is often sold as packs of two, because of this dual-channel feature modern motherboards have. It is important to add the memory modules in the right slots to benefit from the dual-channel feature. In a motherboard that has four DIMM slots, two of them are usually the same color and the other two are some different color. The first channel is usually the slots 1 and 2. The second channel is then the slots 3 and 4. Basically, you need to know only the following.  The slots 1 and 3 are to be used if you install only two memory modules. If you are going to add other two modules, you have to put them in the remaining slots 2 and 4.

When buying RAM, make sure that the DDR version is the right one, so it will actually work in your build. Another thing to look for is the amount of RAM your motherboard supports. This will affect the how much RAM you can have in your system, but also the amount of RAM per memory stick. Many motherboards support 64 GB of RAM, that means 16 GBs per memory stick. Most people won’t have more than 16 GB of RAM in their system. Make sure that your motherboard supports the amount of RAM you need and that you won’t buy more than you can use.

Amount of RAM you need

As said, most people who build computers will go for 16 GB of RAM, which will usually be more than they actually need. Normal users won’t need more than 8 GBs of RAM for their systems. With normal user, I mean someone who doesn’t run, for example, virtual machines or any other program that is handling large amounts of data. Enthusiast can have even 64 GBs of RAM in their systems, needed or not.

One thing that is important to mention is that you don’t have to go straight for the 32 GB or even 16 GB of RAM if you aren’t sure how much you will actually need it. Or if your budget is tight and can’t afford more RAM at the moment.

You can first go for 8 GB of RAM and later upgrade it to 16 GBs if needed. I suggest getting the RAM sticks as pairs, it is possible to use only one RAM slot at a time, but it is not recommendable. What you should do instead is to get two 4 GB RAM sticks and install them both the same time, as I have mentioned earlier. As a downside, if your motherboard has four RAM slots, you can only upgrade your system to 16 GBs. If you are planning to upgrade your system to a higher amount of RAM later, you should start with two 8 GB RAM sticks. This way you can still go up to 32 GBs of RAM.

Before purchasing any RAM at all, you should know what type of RAM you need and how much. Otherwise, you will run into problems installing the RAM in the DIMM slots and you can’t really plan the future upgrades of your PC.

Two old DDR3 RAM modules

Two old DDR3 RAM modules.



Another thing to check when buying RAM for your build is that the RAM modules aren’t too high. The height of the RAM depends on the manufacturer and sometimes it might be too much, and your RAM won’t fit in the slot because the CPU cooler is blocking the slot. So, when selecting the cooler for your CPU, keep the height of your RAM in mind and make sure that both components will fit nicely. Some coolers have been modified to give more space for the RAM.


The speed of RAM modules is measured in MHz, it means the number of clock rates in a second. Simply, the higher the clock speed is, the faster the memory is and the more work it can get done.

The speed can also be measured in the Column Access Strobe Latency (CAS, CA, CL or sometimes only C), of the RAM has, but this isn’t that common at all.  The latency of the RAM can also be measured in few ways, so it is better to compare the RAM modules with the MHz than latency. Not all sellers even mark the latencies in the advertisements, so it is sometimes impossible to compare the latency of the RAM’s.

The standard speeds for RAM are regulated by JEDEC Solid State Technology Association. JEDEC means Joint Electron Device Engineering Council, it is a council which regulates different memory types. In this case, JEDEC has some regulations affecting the DDR3 and DDR4 memory versions.

JEDEC has standardized 2133 MHz as the stock speed for DDR4 modules, this means that RAM modules with overclocking capabilities will work at 2133 MHz before the actual overclocking. However, some high-end motherboard, processor and RAM combinations are supporting 2400 MHz and some even 2666 MHz out of the box, this is without overclocking at all. Depending on the RAM and motherboard, you can then overclock it to even higher speed that is supported by both of the components.

Close-up of a RAM module

Close-up of a RAM module.



Your RAM must be capable of running at higher speeds than the stock speeds, it is often marked in the ads. To be able to overclock easily, your motherboard needs to have Intel Extreme Memory Profile (Intel XMP) and in this case, your RAM needs support XMP as well, these are usually mentioned in the motherboard and RAM listings. If you are using AMD compatible motherboard and AMD processor, just make sure your motherboard has advanced BIOS to manage RAM overclocking, this is just to make sure that you can access the settings related to overclocking. The ads for motherboards with AMD socket usually mention if the motherboard can be used with RAM that is running at higher than stock speeds.

As with all overclocking, you might, or might not get the results somebody else got with the exact same setup also remember to be careful not to break your components. I suggest that you try to find out the spot where you can get benefit from overclocking but still aren’t at the high, unstable end of the RAM’s capability to be overclocked.

Most stable RAM overclock setups with the most benefit are usually around 3000 MHz to 3333 MHz, but it really depends on the other components as well.For example, there is a point where your processor won’t be able to keep up with the speed your RAM is able to input data into it. Beyond that point, it’s not reasonable to waste time and resources to achieve a maximum point of the RAM speed.

DDR4 modules consume 1.20 V and DDR3 modules consume 1.5 V normally. If you are going to overclock your RAM, the clock speed will be higher, but also the power consumption will be higher. Of course, you are able to achieve better performance with the cost of higher power consumption and heat dissipation. It isn’t hard to understand, that when the power consumption is higher than usual, the RAM also produces more heat than before.


Many RAM sticks have the circuit board covered with some colorful plates. A lot of people think those are there just for the looks, but they actually make the RAM cooler. Cooling is always important when overclocking and RAM is not an exception. If you want to overclock your RAM, remember to buy modules with cooling plates around the actual RAM, this will improve the cooling and helps you to achieve your overclocking goals more easily.

Kingston RAM with a cooling plate

Kingston RAM a with cooling plate.

Error correction

Error-Correcting Code Memory (ECC Memory) is a type of memory, which is capable of detecting and correcting common data corruptions. Error-correcting memory is commonly used in computers where a single error can have huge impacts. For example, scientific studies, where an error can change the end result and later have bigger results. ECC memory is not used in consumer computers, it is available for purchase, but it is more expensive than non-ECC Memory. Some non-ECC memory is able to detect errors, but not correct them.


If you have a computer case with a tempered-glass panel, you might want to think the colors of your components. While RAM isn’t the biggest and the most prominent component, depending on the panel, you probably still can see it. Gladly, there are colorful RAM modules and even modules with RGB lighting on them. This way you can add some color to your design. You can make the RAM match the color scheme of all the other components or have the RGB lights on a certain color.



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About the author

PC Rookies is a one-man-project to offer basic information about computers. The writer is studying computer sciences and a computer hobbyist.

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