What to Know When Buying Computer RAM

While RAM (random access memory) can be easily sourced, finding the correct RAM compatible with your system can prove to be a bit more challenging especially for just the average user.

If you are looking into upgrading the RAM in your PC or laptop it’s important to ensure you are sourcing the correct RAM for your system. Take some time and do your research first on exactly what it is that you are looking for. This tech tip outlines the important information required to help you address questions you may have when purchasing the correct RAM for your system.

Type of RAM

The first think to think about when buying RAM is what type you will need. There are many types of RAM available for you to choose from such as SDRAM, DDR, DDR2, DDR3, DDR4, etc. Pick the right one.

EDO DRAM

It stands for Extended Data Output Dynamic Random Access Memory. It Was a big improvement to earlier versions of DRAM as it was able to retain data for a longer period. Unlike conventional DRAM which can only access one block of data at a time, EDO RAM can start fetching the next block of memory at the same time that it sends the previous block to the CPU. This allows it to be possible for programs to be executed sequentially without any delay.

SDRAM

Stands for Synchronous Dynamic Random access memory. The word synchronous refers to it’s synchronization feature with the system bus. This allows it to run twice as fast as EDO DRAM. One of the major disadvantages of using SDRAM is that it works in Single Data Rate which allows it to carry out only a single task per clock cycle. Due to this disadvantage of SDRAM, Double Data Rate SDRAM was introduced.

DDR SDRAM

Double Data Rate (DDR) is capable of processing two read and two write instructions per clock speed. DDR SDRAM provides better speed than SDRAM whilst consuming a lesser amount of energy.

DDR2 SDRAM

In 2003, DDR2 SDRAM emerged. It’s performance is better than DDR as it’s input/output buffer frequency is doubled and can run at higher clock speeds.

DDR3 SDRAM

Double Data Rate Type 3 Synchronized Dynamic Random Access Memory.  DDR3 memory was released in 2007 and doubles the speed of DDR2 while yet again using a lower power consumption. It improves on performance from the DDR2 SDRAM through advanced signal processing, greater memory capacity and can also run at higher clock speeds. It is the one which is most common in PCs today but is now slowly being surpassed by DDR4 in newer machines.

DDR4 SDRAM

The latest RAM that can be found in new PCs today is called DDR4 RAM. DDR4 stands for Double Data Rate Type 4 Synchronous Dynamic Random Access Memory. This RAM is a higher speed successor to the technology used by DDR3. This provides better system level reliability, capacity, performance scalability and power efficiency in comparison to the previous DDR3.

How to read the labelling on the RAM – PCX-XXXXX

When reading the labelling on RAM sticks it can be confusing. You will often see numbers like PC-XXXX or a speed reading of either 100Mhz or 133Mhz The speed readings are not always the most effective way to express the unit’s speed. Thanks to the doubled data rate speed, a DDR DIMM rated at 100 MHz can actually perform 200 million data transfers in a second. Because of this, a 100 MHz DDR DIMM is actually runs as DDR-200, a 133 Mhz DDR DIMM runs as DDR-266, and so on. It is imprtant that if you are to install an additional RAM stick that the speeds of your stick should always be the same.

DDR DIMM PC ratings (PCXXXXX) can be calculated by multiplying the rate of transfers per second by 8, which would give DDR-200 a PC rating of PC-1600. If you can not find the speed but can find the PC rating then divide this by 8.

DDR3 DIMMs are even faster yet, with the most basic model run four times as fast as DDR DIMMs and are capable of 800 million transfers per second. These DIMMs can reach speeds of 6,400 MB/s and are labelled DDR3-800 and rated PC3-6400.

Unbuffered and Fully-Buffered

RAM can be either unbuffered or fully-buffered, also known as unregistered or registered. Buffered RAM has an extra piece of hardware that unbuffered RAM does not, called a register. The register is located between the memory and the CPU. When running, it will store or “buffer” data before it is sent off to the CPU. In systems with large amounts of memory or an extreme need for reliability, buffered RAM is used more often than not, sometimes even in conjunction with ECC RAM. Unbuffered RAM, on the other hand, does not have a register to buffer data before it is sent to the CPU. Rather than being intended for use in servers or other large systems, unbuffered RAM is perfectly capable in a personal computer.

Buffered or registered DIMMs are referred to as RDIMMs, while unregistered DIMMs are referred to as UDIMMs. When buying RAM this is not a crucial thing to look at but good to know. Unbuffered is perfectly fine for a home PC.

Frequency

Always check with the documentation from your motherboard first before looking at which RAM you will require. Your motherboard will only accept certain frequency of RAM, such as up to DDR3 1600MHz for example. If you go an buy a stick of RA that runs at a faster frequency you’ll be forced to run it at a slower pace or it might not work at allPick slower memory and you will limit your system performance. As a general rule of thumb, higher frequency means higher performance, but other factors such as timings weight in too.

QVL – Qualified Vendors List

This is a tip that not many people may know. When buying RAM check the Qualified Vendors List on your motherboards manufacturer’s web page. This will state which RAM was tested and is guaranteed to be compatible with your motherboard.

How much RAM do you need?

That really depends on your needs, although I tend to recommend at least 8GB as a standard for any system, 16GB for a high performance system. You could easily go as low as 4GB if you are just using your machine for Internet surfing and word processing. You would need at least 8GB to 16GB for any gaming system if you want to run modern games.

32 or 64 bit?

32 bit operating systems can only address up to 4GB of memory in total, including the memory on your video card and within your CPU. If you plan on using more than 4GB, you’ll have to use a 64-bit OS in order to be able to take advantage of all your RAM. Most machines these days will come with 64bit OS to cater for the larger RAM sizes.

How many sticks of RAM do you need?

Most PCs will have a maximum of 4 available slots. Using two sticks is preferred over four, as it’s easier for your motherboard or CPU memory controller to handle only two sticks and this will also leave room for an upgrade in the future if you have spare slots. Four sticks can be a nightmare when it comes to compatibility and will also limit your RAM frequency and/or timings when it comes to overclocking

Warranty

Some manufacturers offer a lifetime warranty. Some let you increase your voltage under warranty. RAM tend more to be faulty when you receive it/buy it then after several years, so it’s a good idea to buy it from a vendor who allows for easy and painless RMA process.

Conclusion

With your RAM needs completely dependent on your system and how you intend to use it, knowing what your system needs to run smoothly is the most vital step when shopping for RAM. Hopefully some of the above information will help when it comes to understanding the different types of RAM that is available.  Often times, computer RAM chips will fortunately not fit into slots in systems they are not compatible with; sometimes they do. Shoving a module that is not meant for your system into a slot can be as harmless as causing you minor annoyance, or it can also be as harmful as causing hundreds of dollars worth of damage.

Before buying RAM, take a look at your computer and the motherboard’s manufacturers web site for approved vendors and specifications for your computer. Be sure you know what you have, and also know what you need. You have the power to upgrade your system as you please, but you also have a responsibility to know what your upgrade requires.

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