Computer Memory Buyers Guide
What is RAM / Memory ?
System memory, or more accurately RAM (Random Access Memory) is used by PCs to temporarily store data before it is permanently stored on a storage drive. The more memory your system has the more applications it can run at once and the faster those applications will run.
With hundreds of models of memory available at any one time, it is important that you choose memory that is compatible with your system. It is also worth considering what you are planning to use your PC for, as different games and applications will benefit from varying amounts of memory.
While there are dozens of different memory manufacturers, Scan recommends CORSAIR MEMORY as it is extremely reliable and available in a wide range of models.
Which type of memory is right for my system?
While there are various types of memory available, the vast majority of PCs sold in the last few years support a couple of types of memory – DDR4 and DDR5. This stands for Double Data Rate, with the ‘4’ and ‘5’ meaning this is the fourth or fifth generation of DDR memory. Don’t panic though, if you have an older system that isn’t compatible with DDR4 or DDR5, Scan still stocks a wide range of DDR, DDR2 and DDR3 memory.
The handy table below summaries which type of memory is best for the most popular platforms, but it’s best to check the specs of your CPU and motherboard as whether they support DDR4 or DDR5 as this can vary from system to system.
| CPU | DDR4 | DDR5 |
|---|---|---|
| Intel 14th gen Core | ✓ | ✓ |
| Intel 13th gen Core | ✓ | ✓ |
| Intel 12th gen Core | ✓ | ✓ |
| Intel 11th gen Core | ✓ | ✖ |
| Intel 10th gen Core | ✓ | ✖ |
| AMD 4th gen Ryzen | ✖ | ✓ |
| AMD 3rd gen Ryzen | ✓ | ✖ |
| AMD 2rd gen Ryzen | ✓ | ✖ |
| AMD 1st gen Ryzen | ✓ | ✖ |
Things to Consider with Memory
| Size | The next thing to consider is what size memory you should be looking at. Most desktop PCs require memory sticks, known as DIMMs, each with 288-pins on them. However, if you’re trying to upgrade a laptop it will require SODIMMs, these are a bit stubbier than standard DIMMs, and have 240-pins. |
| Channels | The second decision you need to make is selecting a pack of memory with the optimum number of channels. All modern CPUs are capable of running multiple DIMMs together to boost performance. Most CPUs support dual-channel memory, so will perform best when you install the memory in pairs; however, some high-end CPUs support quad-channel memory, so will perform best when you install the memory in multiples of four. Although you can buy multiple individual DIMMs, it is better to buy a dual-channel or quad-channel kit, as the individual DIMMs in the pack will have been tested together by Corsair. |
| Speed | The final consideration is the speed of the memory. While there are a number of factors that determine memory performance the most important spec to look out is the speed, which is displayed as the frequency in MHz. A word of caution, you won’t get the full benefit of high frequency RAM unless you go into the motherboard BIOS and do some tweaking. This is because not all CPUs support super-fast memory, so MOTHERBOARDS set the memory to run at a safe neutral speed out of the box. Think of it liking starting a car engine in neutral rather than first gear. For most CPUs, this neutral speed is 2133MHz, so if you’re intending on buying much faster memory, don’t forgot to configure the BIOS according once you’ve installed your new RAM. |
| Aesthetics | Now that you know which type of memory is right for your system its worth quickly pointing out that you also have a choice of the appearance of the DIMMs, including the latest fad, memory with built-in RGB lighting. |
Size
The next thing to consider is what size memory you should be looking at. Most desktop PCs require memory sticks, known as DIMMs, each with 288-pins on them. However, if you’re trying to upgrade a laptop it will require SODIMMs, these are a bit stubbier than standard DIMMs, and have 240-pins.
Motherboard Compatibility
Make sure you check that your motherboard supports the type of memory that you’re going to use, most likely DDR4 or DDR5. While some CPUs support both types of memory, motherboards will only support one or the other.
Channels
The second decision you need to make is selecting a pack of memory with the optimum number of channels. All modern CPUs are capable of running multiple DIMMs together to boost performance. Most CPUs support dual-channel memory, so will perform best when you install the memory in pairs; however, some high-end CPUs support quad-channel memory, so will perform best when you install the memory in multiples of four. Although you can buy multiple individual DIMMs, it is better to buy a dual-channel or quad-channel kit, as the individual DIMMs in the pack will have been tested together by Corsair.
Speed
The final consideration is the speed of the memory. While there are a number of factors that determine memory performance the most important spec to look out is the speed, which is displayed as the frequency in MHz. A word of caution, you won’t get the full benefit of high frequency RAM unless you go into the motherboard BIOS and do some tweaking. This is because not all CPUs support super-fast memory, so MOTHERBOARDS set the memory to run at a safe neutral speed out of the box. Think of it liking starting a car engine in neutral rather than first gear. For most CPUs, this neutral speed is 2133MHz, so if you’re intending on buying much faster memory, don’t forgot to configure the BIOS according once you’ve installed your new RAM.
Aesthetics
Now that you know which type of memory is right for your system its worth quickly pointing out that you also have a choice of the appearance of the DIMMs, including the latest fad, memory with built-in RGB lighting.
How much memory do I need ?
Installing more memory in your PC or laptop is an easy way to boost its performance, however, not all applications and games will benefit from having lots of memory. The following tables shows several examples of different uses for a PC, giving examples of how much memory will give you the best bang per buck. You can of course install more memory, but the aim of this guide is to show you the optimum configuration so you don’t spend more than is necessary.
Home & Office
Web browsing, email, Youtube etc
Run several applications at once
Edit photos in Adobe Photshop
Gaming
Games like Minecraft and DOTA 2
Games like Call of Duty and GTA V
Live streaming games
Graphics Workstations
Design applications
Visualisation applications
Simulations, visualisation with large models and textures
Audio Workstations
Small sound libraries
Mid-size sound libraries
Large sound libraries
Video Workstations
Working with FullHD video
Working with 4K video
Working with 4K or higher video
Server Memory
There are a number of key things to consider when choosing server memory modules. Firstly is how many you choose - filling up the server with low-capacity memory modules, means you will not be able to add memory modules in the future. You will have to remove the existing memory modules and buy new ones to achieve maximum capacity. Furthermore, the greater number of modules you have will draw more power and if all the slots are full the memory speed will be capped as the high number of modules are all accessed. A better configuration is a smaller number of larger capacity modules, meaning better performance and room for expansion if required.
Second, is the type of memory or DIMMs (dual inline memory modules) to choose.
UDIMM
UDIMM or Unbuffered DIMM acts so the address and control signals can directly reach the DRAM chip on the server DIMM without going through a buffer and without any timing adjustment. When data is transmitted from the CPU to the DRAM chips on the DIMMs, the UDIMM needs to ensure that the transmission distance between the CPU and each DRAM chip is equal. UDIMMs are lower in capacity and frequency and have lower latency - however, UDIMM cannot maximise server performance because it only operates in unbuffered mode and thus cannot support the maximum RAM capacity.
RDIMM
RDIMM or Registered DIMM attaches a register between the CPU and the DRAM chip for data transmission, which reduces the distance of parallel transmission and improves transmission efficiency. RDIMMs are easier to increase in capacity and frequency than UDIMMs due to their high register efficiency. Moreover, RDIMM supports buffered and high-performance registered mode, making it more stable than UDIMM. This gives it the highest-capacity server RAM performance and a wide range of applications in the server RAM market.
LRDIMM
LRDIMM or Load Reduced DIMM do not use registers but are simply buffered. The buffering reduces the power load on the underlying motherboard but has little effect on memory performance. The direct benefit is to reduce the server memory busload and further increase the server RAM support capacity. This not only reduces the load and power consumption of the memory bus but also provides the maximum supported capacity of server RAM.
ECC DIMM
Error Correction Code or ECC memory uses a mathematical process that ensures the data stored in memory is correct. In the case of an error, ECC memory also allows the system to recreate the correct data in real time. ECC uses a form of parity, which is a method of using a single bit of data to detect errors in larger groups of data, such as the typical eight bits of data used to represent values in a computer memory system. ECC memory looks different to non-ECC memory as it has an extra chip that performs the ECC calculations. It has particular value in a business environment as its ability to detect and correct memory errors helps fight data corruption and reduce system crashes and outages of servers and datacentres. ECC memory must be matched otherwise the error correcting capability will be lost. ECC memory is not always registered or buffered, however, all registered memory is ECC memory.
Persistent Memory
Regardless of registering, buffering and error correcting, all traditional DIMMs will lose their data should power fail or the server crash. Persistent memory (PMEM) is a newer technology drawing on a combination of memory DIMM and SSD storage that allows for data to be secure if the power fails but also to bridge a gap between system memory and storage.
PMEM offers numerous advantages like lower access latencies, supporting larger datasets and hardware encryption and when compared to DRAM, PMEM modules come in much larger capacities and are less expensive per GB, however they are still more expensive than NVMe.
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