How to Choose a RAM?

Random Access Memory or RAM is the primary temporary storage area of a computer. It consists of rows and columns that are accessed randomly rather than sequentially as you would find on a hard drive.

When your computer runs out of space, it will first start to store things in one of the following types: virtual memory, page file, swap files, or even on your SSD/HDD if you have enough room on them instead, but these all function much slower than simply adding more physical RAM to your build.

Important RAM Specs

Capacity:

The size of the capacity will be determined by the amount of data that you need to store, transfer, and process. The larger it is, the more RAM you’re able to have and the faster your computer will run.

Storage & Transfer speed pertains to read/write speeds for information transfer though it’s worth noting that only a few programs can take advantage of high memory bandwidth so there’s not much point in having massive amounts if they won’t be utilized.

High-end workstations would use 16 GB+ whereas gaming rigs may go as low as 4 GB or even less while basic home computers don’t generally exceed 8GB. If you are on the fence about what capacity you should get, opt for 8 GB.

RAM size can be measured in Gigabytes (GB) and is usually combined with a memory speed to accurately describe performance:

Speed:

The speed of your RAM will play an important part in how smoothly your computer performs. Go with the minimum supported RAM speed required by your Operating System otherwise it may cause system crashes/blue screens or be unable to start up at all! When choosing this kind of hardware consider that frequency also matters more than capacity which we’ll discuss next.

Frequency is related to the time taken for information transfer. The higher the frequency, the better it is because data can be transferred faster. RAM speed may be measured in either Megahertz (MHz) or Gigahertz (GHz).

Latency:

The response time of RAM is determined by the size of the storage cache. Having more (smaller) pieces of memory that can be accessed a lot faster is better than having fewer larger ones because it drastically increases read/write speeds.

Memory Latency can be measured in 2 ways: CAS Latency & RAS to CAS Time. We will focus on the latter which also falls under Command Rate since it’s directly tied to gaming performance:

CAS stands for Column Address Strobe, this determines how long you have to wait for a column address and how many clock cycles are needed between each.

RAM Command Rate is most often measured in nanoseconds. (a billionth of a second). The lower this value, the faster your RAM will perform because more can be done in less time.

Multi-Channel:

If you are using more than one stick of RAM without the proper number of independent channels then performance will be limited since bandwidth is shared. For instance, if each stick has a maximum speed of 1600 MHz and the Dual-channel configuration requires two sticks to achieve its full potential, only one RAM stick can run at that frequency so in this case, both sticks would be running at 800MHz.

RAM can use either single or dual channels for their configurations which improve performance by allowing data transfer between multiple pieces of memory simultaneously.

This allows RAM to work together as a larger overall capacity which in turn speeds up information transfer while simultaneously increasing efficiency and reducing wasted bandwidth.

The optimal situation would have all four slots filled with one piece of dual-channel RAM per channel.

If you have a system with 4 slots then I strongly recommend going for a quad-channel configuration which would require at least four sticks of RAM.

Latency Timings:

Latency timings are a measure of how much power it takes to get data to the RAM. If your system can have all four slots filled with dual-channel RAM then you should consider going for lower latencies since they improve overall performance. 

Dual-channel configurations also benefit from lower latency timings because bandwidth is shared between 2 sticks. For now, just know that higher numbers mean a longer time in which an action will be completed which in turn makes things slower.

The DDR standard dictates these times so if you see them listed on the product description make sure they match those set out by the manufacturer otherwise processors won’t be able to access information properly.

RAM bandwidth is used when multiple memory modules operate together to perform multiple tasks at the same time. The more you have, the better it is however if there isn’t enough then RAM will have a hard time keeping up.

CAS Latency:

The speed of your memory module’s CPU. The lowest possible value that offers performance gain for any given clock frequency so even if you raise the clock this will still drop in value and vice versa, lower it too much and bandwidth problems will arise where results will become inconsistent or impossible to predict since modules can’t run at their most efficient speeds anymore.

For gaming systems I recommend 8 or less with an I5/I7 processor otherwise games may not be playable because they won’t load properly or crash after some time! In general CAS latencies of 10 or less are considered ‘ultra’ low for gaming systems.

RAS to CAS (tRCD):

The number of clock cycles that must take place between the time a command is issued and its execution. The lower this value, the better performance will be because there’ll be less waiting around for operations to finish which in turn makes everything faster. 

RAS Precharge Time:

How long it takes before RAM can accept another command from the processor or any other source which again improves overall performance since information transfer doesn’t have to wait around as much.

Read Delay:

the amount of time needed by a system with multiple memory modules installed before accessing data on a different module after completing its operation on the current one. This is due to a process known as ‘page swapping which takes place when RAM access is required and multiple slots are used. In this case, the memory controller will look at the system’s page table to find out which module should be accessed next.

This value indicates how long a processor has to wait to get access after completing its operation on one stick before it can start working on another. The longer this time, the better performance will be since information transfer doesn’t have to wait around as much between modules.

Read Rank Write (tRRWT):

The amount of time needed by a system with multiple memory modules installed before accessing data from different sources as well as writing it back onto a different module again. This is due to a process known as ‘page swapping’ which takes place when RAM access is required and multiple slots are used. In this case, the memory controller will look at the system’s page table to find out which module should be accessed next as well as where information from that RAM location is going to be written for it to remain consistent across all modules of a system.

This value indicates how long a processor has to wait to get access after completing its operation on one stick before it can write onto another (the module which data will be written into again). The longer this time, the better performance will be since information transfer doesn’t have to wait around as much between modules.

CAS Write Delay:

Well, you know what they say about 4 sticks being better than 2. This is a method to make sure that each stick gets a chance to send its data across so as not to compete against itself and lose out on performance. There will only be problems if you run a system with 4 modules at the same time and/or don’t have any type of RAM controller in your motherboard or processor otherwise everything is fine. Just avoid running quad-channel systems with 2x2MB DIMMs for optimal results!

These values are also crucial for gaming systems so stay away from settings like tWRWT: 5, tRAS: 32 which are meant for high-end multi-core workstations.

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