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How to Choose RAM: Speed (MHz/CL) vs Capacity (GB)

Assumptions about RAM
RAM: Why Not Speed and Capacity?
«More RAM means more speed» — Debunking a classic assumption
RAM: Speed and Latency (CL)
Does speed really make a difference?
Intel vs AMD CPUs
- Intel
- AMD
Overclocking
- Motherboard QVL/Memory support lists
Module quantity and capacity
Achieving stability
What if you want it all?
Conclusion

Assumptions about RAM

As a general rule, the faster the speed, the better the performance of RAM. But, as we’ve stated above, there’s a little more to it than that. In fact, the fruits of high-end memory aren’t available without some trade offs — especially if you want to install a large capacity of RAM.

So, we’ve put together this guide which will take you through the specifications of memory and ultimately help you to decide, when you’re looking for RAM, whether you should be buying for speed or larger capacity.

Note — this guide has been written with regards to DDR4, however the general concept should translate to the upcoming DDR5 standard, just as it does with older standards such as DDR3.

RAM: Why Not Speed and Capacity?

For the most common RAM speeds out there, you’ll be able to get the capacity you want at a decent speed.

Unfortunately though, if you’re looking for a large quantity of memory at a high speed (for example 64GB at 3600MHz), this isn’t a realistic proposition.

Many people underestimate the resources required to pull off this combination of large capacity and high speed. Where it can be pulled off, sacrifices have to be made elsewhere in your system.

But, why is this the case? Well, this guide aims to provide you with the answer.

TLDR — if you want the answer, skip to the conclusion. However, if you want the full details, keep reading.

“More RAM means more speed” — Debunking a classic assumption

Time and time again we speak with customers who assume that the larger the RAM capacity, the faster the system.

This assumption is false and originated many years ago, back when computers and laptops were equipped with smaller RAM capacities. Back then, most operating systems and applications were generally using a larger proportion of the average installed RAM capacity for most machines, and therefore slowing the system down. To fix this, adding more RAM was usually the answer.

Today, however, most machines are fitted with 8 or even 16 gigabytes of RAM and usually run without any issues. The reason? The operating system’s RAM usage is proportionally lower on newer hardware. As a result, there’s no need to increase the system’s RAM.

Of course, this doesn’t apply to absolutely everyone.

For the average consumer, there’s a rule which will help them understand if they need more RAM:

Adding more RAM will only boost your system’s speed if it’s using all the capacity that is currently installed.

For anyone buying or building a PC right now, this is a great nugget of knowledge to retain. If you can calculate your RAM requirements before you buy (and therefore avoid buying more capacity than you need), you can allocate the money you save to something with a larger innate performance, which leads nicely onto the next section…

RAM: Speed and Latency (CL)

RAM can be purchased in a variety of speeds, with differing latencies.

Unless you’re a true enthusiast, there are mainly two key specifications of a RAM module/kit (other than capacity) that you should pay close attention to:

• Memory frequency (MHz).
• CAS Latencies (CL).

You need to look at both specifications in order to get a good indication of the RAM’s final performance. As a general rule, you should consider the following (for those of you who are interested, we’ve added the formula below):

The higher the speed, and the lower the CL, the better the overall performance.

RAM latency (lower the better) =

CAS Latency (CL) x 2000

Frequency (MHz)

So, the money you’ve saved from not purchasing that larger capacity RAM kit should be used on the best performing RAM right? Well, before you do that, let’s discuss the drawbacks of hyper-fast memory and whether all kits with faster speeds are worth the money.

Does speed really make a difference?

The short answer is yes. But, the long answer is — it depends on a few factors.

Your workload will ultimately decide whether speed will make a difference for you. For people who use CPU-heavy applications, faster RAM will certainly make a difference.Whereas home users don’t need to worry about RAM speed too much. But, what about gamers who fall in between these two groups of people? Well, that depends on the gamer’s choice of CPU.

Intel vs AMD CPUs

Intel

Intel CPUs aren’t massively reliant on the performance of memory while running, which might explain why RAM speed support has historically been rather limited outside of Intel’s enthusiast chipsets (Z-Series) and capped to 2666Mhz (at least until recently).

If you’re the owner of an Intel CPU we certainly suggest getting a good quality RAM kit, but the speed of that RAM isn’t as important. Save your money for other components or a RAM capacity upgrade if required.

AMD

In stark contrast to Intel, AMD’s more recent ‘Zen’ line of CPUs has RAM speed almost baked into the architecture of the CPU.

AMD’s infinity fabric technology uses the speed of the RAM to pass information across sections of the CPU. This means that better memory will serve to boost the CPU performance as well as helping in those intense applications we mentioned earlier.

There is another factor to consider which is the FCLK speed and the ratio between that and the RAM itself — but that’s a topic for a separate article.

But, in summary, a high-performance 3600MHz memory kit is ideal for AMD Ryzen CPUs.

Overclocking

Did you expect overclocking to appear in a guide to RAM? Probably not, but to address the elephant in the room, most RAM speeds over 2933MHz are technically classed as overclocks.

This classification is usually set by your motherboard. For example, if you’ve ever checked your motherboard specifications, you might find that the speed of your average gaming RAM (3200MHz) is marked with a little ‘OC’ (overclocked) sign.

Whenever you activate the XMP or DCOP memory profile in your BIOS, you’re loading a preset bank of BIOS settings specifically for your memory which matches the advertised speed and CL. Once you save these settings, you could well be running your RAM above factory specifications.

The problem?

Overclocking any component above factory specifications has the potential to cause system stability issues, or even a boot failure. The further you push your system, the higher the likelihood of instability becomes.

This is the reason you should take a more measured approach with memory and review your choice of motherboard and CPU, rather than just buying the fastest RAM kit available. Just as you wouldn’t buy a budget motherboard to overclock a CPU, the same concept should be considered when it comes to RAM (but with slightly less significance).

Motherboard QVL/Memory support lists

Many manufacturers list specific RAM kits as ‘verified’ with their products, meaning that the manufacturer has tested the motherboard model in question with a specific RAM kit and has confirmed full support for that kit, at its advertised speed and CAS latency.

CCL advises that you purchase RAM listed on your motherboard’s QVL where possible, for the best compatibility. However, this is almost always impractical given the availability of exact RAM kits at any given time.

Module quantity and capacity

Now that we understand that high-speed RAM runs your system in an overclocked state, we can begin to piece together why people should ‘choose’ between speed and capacity.

Just like memory speed and CAS latency, module quantity and capacity are both factors that, when increased, will add to the stress of an overclocked system.

Luckily, the greater availability of RAM can help offset this problem slightly, as kits with larger individual modules can help eliminate the added stress of having many RAM modules installed at once. Larger RAM kits do this by compressing the capacity into a lower number of modules.

This isn’t a guaranteed failsafe, but it can sometimes make the difference between a system successfully booting or not.

Achieving stability

Speed, CAS latency, module size, and module quantity; in order to avoid running into problems you should balance these factors when considering your purchase.

For example, 16GB of 3600MHz CL16 memory is much more likely to be stable than 32GB of the same modules, even if the settings in BIOS remain the same.

Consider another example — you may want to run 64GB of RAM at 3600MHz, but to get it to run properly you need to lower the speed to 3000MHz.

We can condense this balancing act into a simple choice triangle (although speed and CL can technically be put in the same class — hence the title of this article):

PICK TWO

What if you want it all?

It’s certainly possible!

A high-end motherboard features a more reliable power delivery design and a thicker PCB, which can be used to supply cleaner voltage to the RAM and regain some of, if not all, of the stability that is lost when applying a RAM overclock.

Generally, we find that motherboards of this class are in excess of the £250 mark, but that’s not always the case. The best thing is to do some research on your board. Freel free to contact our sales team or check out our motherboard buying guide; either way, we’ll be happy to help you choose.

Conclusion

So, to bring everything together, we can conclude that your choice of memory can be condensed into two, easier to understand, components:

Performance (speed) vs Stability (capacity)

You should keep in mind our earlier reference to Intel vs AMD CPUs as this will affect consumers differently based on their choice of CPU. We suggest that unless you’re a real computing enthusiast, you should stick with stability (unless you want the occasional headache of system crashes).

For your convenience we’ve included a handy combination table below that will give you a rough idea of what speeds you can generally achieve whilst retaining solid stability using a mid-range motherboard and chipset (example used is an MSI MAG B550M MORTAR motherboard; results may differ from board to board):

		Total RAM capacity
		8 GB	16 GB	32 GB	64 GB
Number of modules installed	1	3600 MHz	3600 MHz	3200 MHz	2933/3000 MHz
	2	3600 MHz	3600 MHz	3200 MHz	2933/3000 MHz
	4+	3200 MHz	3200 MHz	2933/3000 MHz	2666 MHz

For those of you who want both high speeds and capacity, a quality motherboard, knowledge of overclocking and a good amount of patience is what you’ll be needing.

We have a great range of motherboards available here, and can offer further sales advice via email or telephone.

3 Ways to find Accurate CAS Latency (CL) Ratio of RAM

Are you one of those who searched a lot about CAS Latency (CL) ratio? Still unsure about the exact meaning & where to locate it? Don’t worry, we will try our best to explain it.

CL Ratio is crucial when purchasing add-on RAM. It plays a significant role while upgrading or replacing current RAM modules. RAM with different CL numbers can hinder achieving optimal performance.

If you need better information about CAS latency ratio, then navigate towards methods to find out CAS latency ratio.

Before diving into the definition, let us see what the full form of the CAS.

CAS ➔ Column Address Strobe

I bet; you may still be skeptical about CAS latency ratio. Since, the full form does not reveal any understandable meaning.

Don’t worry, why are we here? We are doubt solvers. ? Let’s look at CAS latency ratio step by step.

CAS latency (CL) can be defined as the time gap between the read command initiated by memory controller and the moment when data is made available by the RAM.
Simply, it’s delay to produce a data by column of RAM.

Thus, a lower CAS latency ratio denotes better performance. However, not only the CAS latency ratio but the clock speed, rank, DDR generation, ability to overclock and other factors are crucial while predicting performance. That’s why Doubt Solver recommends using RAM with the same CL ratio & same clock speed for the optimum performance.

What is CAS Latency (CL) Ratio?

Now, it’s obvious to have doubt that who is requesting the data for RAM. Right?

I know it’s still beyond understanding, especially non-technical guys.

Before jumping into this technical arena, let me tell a non-technical story.

Non-technical illustration for better understanding of CL Ratio

In above illustration, Manager asking the salesman for a box which contains 3 mangoes. After searching for 2 minutes, the salesman concluded that the box ‘C’ contains 3 mangoes.

In above illustration the time gap is 2 minutes (i.e., time taken to process the request). So, these 2 minutes is nothing but the CAS latency ratio of our illustration.

Now, let’s apply above illustration to real life scenario.

Technical illustration for better understanding of CL Ratio

In above illustration the CAS Latency Ratio is 16.

As you may be aware, CPU processor is the brain of computer.
It processes the datasets supplied by cache memory, known as L1, L2 & L3 cache.
If the required dataset is not available with these caches then the processor orders the memory controller to fetch that dataset from RAM.
Memory controller works as the middleman between processor and RAM.
The memory controller forwards this request to RAM.
RAM processes’ the request and produces the output to memory controller.
This delay between requesting & receiving the dataset is nothing but the CAS latency or CL ratio of that RAM.

CL ratio specified in nanoseconds for asynchronous DRAM. Whereas for synchronous DRAM, the CL ratio is specified in clock cycles.

Right now, a few doubts might come to mind. Some of them are discussed below.

Is a higher or lower CAS latency better?

Lower CAS Latency Ratio is always better than higher CAS Latency Ratio.

Assuming you are choosing multiple RAM with same clock speed (i.e., 3200 MHz x 2 RAM)

Can you mix CAS latency RAM?

Although NOT recommended; technically you can mix different CAS latency RAM modules.

However, the motherboard will match the CAS latency ratio by setting a higher CAS ratio among the installed RAM modules.

For example, you have installer two RAM modules with CL ratio 15 & 16. The motherboard will set CL ratio of 16 for both RAMs. Indirectly, low latency RAM will be degraded to match the higher latency ratio of another RAM.

What is a good CAS latency for RAM?

The performance of the RAM module depends on multiple factors. Such as clock speed, latency ratio, rank etc. So, merely judging RAM on the basis of CAS latency (CL) ratio is not right.

Remember, RAM with a lower CAS latency ratio is always better than a higher one. Lower latency assures the processing of data in minimal time.

Sametime, its recommended to do not mix RAM with different clock speeds or different CL ratios. Otherwise, such RAM modules will not be able to work at their specified speed.

For example, we have two RAM modules with following specification.

RAM Module	Clock Speed	CL Ratio
A	2600 MHz	17
B	2600 MHz	15

Comparing CL Ratios

Which of these would you choose? Right, as per our theory, we will go with a lower CL ratio RAM. Here, RAM module B is faster than A. A lower CL ratio is better.

How do I check my CAS latency?

Here we are giving three methods to find out the exact CAS latency (CL) ratios of memory module.

Method A: via CPU-Z

Follow the below steps to find out CAS Latency (CL) Ratio.

Download CPU-Z application from cpuid.com
Open the app and navigate to the Memory tab
Read the text in front of CAS# Latency (CL)
Done…!

CPU Z

If that CAS#Latency (CL) is 9.0 clocks then your system is currently running on RAM with CL9 Ratio. This means if you want to upgrade the total RAM size without replacing the existing RAM, then you must purchase another RAM with the same CL ratio and clock speed.

How to find clock speed of RAM?

Clock Speed (i.e., 3200 MHz) is also known as DRAM frequency or RAM speed. If you are a Windows 8, 8.1 or 10 user, then you can easily find the clock speed of your RAM without using any utility using the below method

Open Task Manager (Shortcut key: Ctrl + Shift + Esc)
Performance ➔ Memory.

Locating RAM Clock Speed under Task Manager

Moreover, the SPD tab in CPU-Z reveals a detailed report of your RAM. Alternatively, you can Google for the current part number and manufacturer to dig up exact information about your current RAM. It may be helpful to predict the second RAM. Better to choose RAM from the same manufacturer for utmost compatibility. Hope this information will help you purchase your next RAM.

Method B: via Piriform Speccy

Piriform Speccy is another good utility to fetch out CL Ratio. It also reveals tons of information about your device. It could show live uses graphs and temperatures of various components. You can export those details as XML, text file or print / PDF. Just open the app and navigate to the RAM section. Now, you can view Slot information, type, size, CL ratio and much more. See the following screengrab.

Piriform Speccy

Method C: via Command Prompt / DOS

In some cases, installing new software is not permissible due to the administrator’s restriction. or user unable to enter GUI mode (computer restarting in DOS mode). We are writing a solution for you. Thanks to Fazlul Haque, whose comment inspired us to update this post.

Open Command Prompt
1. Press Start + R to open the “Run” window. Write CMD press OK
  or
2. Click on the Start button & type CMD press Enter

Type the following command

wmic memorychip get manufacturer, capacity, partnumber, speed, memorytype, devicelocator, formfactor

It will show information about the installed RAM. Like manufacturer, part number, speed (MHz), device locator (slot), capacity (in bytes), etc.
Now, you have to copy a part number and Google it & get latency ratio information on the manufacturer’s site or shopping sites.

Command Prompt / DOS

Method D: via Inspecting RAM

Laptop RAM

Sometimes the PC / laptop does not turn on. So, the question arises on how to know this CL ratio? At this moment you can do a solution. That is, seeing the information on the RAM itself. This process is simpler if you have a desktop computer. But laptop users have to work a little harder. However, dissembling the laptop is relatively tricky, especially for non-techies.

Anyway, once you notice the pasted sticker of a RAM, you can search for information like brand name, serial number, and model name on Google.

Once the printed serial number matched with searched model number then you can easily access the information. We recommend viewing the information from the official website of the manufacturer. It will assure accuracy regarding specifications.

I hope this post will be helpful for you, to find the compatible RAM. Kindly comment your doubts, suggestions. Or just convey thank you if the above solution worked for you.

what is it, how to change it — a guide in 4 sections

What is RAM timing? What does it affect and how to determine it? Information is in the article. There is also an instruction that shows step by step how this value can be changed.

How RAM works

Its functioning is closely related to the CPU and information media. Data from a hard drive or other storage device initially enters the RAM and only then is processed by the CPU.

The structure of the RAM is similar to a table, where a row is selected first, and then a column. It is divided into banks — SDRAM cells. For example, modern variants of DDR4 differ from DDR3 in twice the number of banks. As a result, productivity increases. The speed of DDR4 reaches 25.6 GB / s, while the bus can operate at 3200 MHz.

To the topic: What is computer RAM, what does it affect: answers to 6 popular questions

0007

These are values that reflect the time over which the data is processed. The indicators look like three numbers going in order. Each number is a time interval, which is measured in bus cycles.

Understand the abbreviations CAS and RAS. The last two letters mean Address Strobe — address strobe signal. Only in the first case it is about the column (Column), and in the second — about the row (Row).

CAS Latency

One of the most significant indicators: it tells how much time it generally takes to find the necessary data after the CPU asks for read access.

RAS-CAS

Indicates the number of cycles it takes to access RAM and activate a row, and then a column that contains the necessary information, and commands to read data or write them.

Useful: What to do if Windows does not see all the RAM: 4 reasons and solutions For this reason, the data contained in it is updated. This is called RAM refresh.

Thus, the RAS Precharge indicator in cycles displays the time interval between the charging signal — RAM regeneration — and permission to access the next line of information.

Row Active

Indicates the time one table row is active before data is read or written.

Note: Command Rate may be used in some cases. It shows how much time is spent on information exchange between RAM and its controller. Typically, this takes one or two cycles.

Useful: How to check RAM in Windows 10: 2 ways Naturally, this also affects the speed of the computer as a whole.

The lower the timing, the higher the performance, the faster the CPU gets access to the banks.

How to find out the timing of RAM

This data, as well as other useful information, can be found by looking at the RAM module itself. Usually they are written on the sticker. Timings are indicated by numerical values. Sometimes the marking contains full information about the latency of RAM, and in some cases only the CL delay. If necessary, all timings can be viewed on the website of the bar manufacturer by entering the model number into the search.

Advice : When replacing or installing additional RAM modules in the system, it is recommended to install brackets in a set, for example, 2 pieces of 8 GB each. Thus, it will be possible to activate the dual-channel memory mode, which will speed up the entire system. But at the same time, it is important that the indicators of both bars are identical. Thanks to this, it will be possible to avoid conflicts between devices that interfere with the stable operation of the computer.

Learn: How to increase laptop RAM in 5 steps: tips and tricks

How to adjust RAM timings

As soon as the user sets the brackets and turns on the computer, the BIOS will automatically learn the frequencies and timings. However, changing the settings of the operative can positively affect the performance of a laptop, PC.

The subsystem provides quite ample opportunities for manipulating the bar parameters. However, the number of editable RAM parameters can vary significantly for different motherboards, even if their chipsets are identical.

On this basis, they can be divided into models with:

Minimal options for changing settings: it is possible to set the frequency of modules and one or two timings. Overclocking options are noticeably limited. A similar phenomenon is the norm for budget class H for INTEL and A for AMD.

Support for editing basic parameters — you can change the frequency, basic timings. This is the standard for most Class B motherboards.

Advanced (marked as Z and X): give the user access to edit the maximum number of parameters.

Warning! It is better to change the values gradually: half a step at a time. You must act carefully, otherwise you can damage the operative.

Note : heatsinks that support XMP are best overclocked.

Addition: How to set up RAM in BIOS: instructions in 4 simple sections

The shorter the timings, the better. If initially they are not as small as we would like, they can be changed by conjuring a little in the BIOS. The main thing is to do everything slowly and after any change, check the performance.

What is the latency of RAM

Some device characteristics may seem insignificant at first glance. But they can affect the speed of information processing in a computer. This also applies to the latency of RAM, which is responsible for the time the processor accesses this equipment to receive data.

What is latency? It is organized

into pages , which store the information you need. To understand which page you can find data on, you should refer to a special table.

The main indicator of the operation of the RAM will be the clock frequency or the number of operations that the components can perform in one clock cycle. But other than that it costs take into account and delays . This is the amount of time the system takes to process a request.

The given value is defined in timings and equates to a millisecond. This is how much RAM time is required before the command starts executing.

So, there are 4 types of delays:

latency (CAS Latency (CL)) , is the most important value that you should pay attention to, shows how much time it takes from a processor request to obtaining information where the necessary data is located ;

RAS to CAS Delay (tRCD ) , transition time from matrix column to row;

RAS Precharge (tRP) , the delay that occurs when one cell closes and another opens;

Active to Precharge Delay , the time it takes RAM to return to waiting for a request.

In some cases, developers only indicate latency. Since this indicator will be the most significant and more affect the overall operation of the computer.

What does it affect?

This indicator will determine the speed of the operation to access the RAM. In today’s powerful computers, it will be difficult to notice the difference in latency. Plus, it’s in milliseconds.

However, this characteristic should not be overlooked when choosing a component. RAM speed should be calculated from clock speed and latency . This is the only way to determine how quickly the processor will receive a response to the requested information, which means how the computer will work as a whole.

Which value is better?

The latent value indicates the time delay for the execution of the operation. This means that, , the lower this parameter is , the faster the processor will receive the necessary information. In this case, the clock frequency should also be taken into account.

There are several ways to find out the characteristics. Timings are indicated by on the RAM board itself. These are 4 digits, which corresponds to the parameters . The first is responsible for latency. In some models, you can find the inscription «CL 11». This means that only latency is indicated here.

If the user does not want to disassemble the computer, you can use special programs:

CPU-Z;

AIDA64;

SiSoftware Sandra.

Utilities are able to display all delays with which the RAM works. In addition, they can be used to test the computer and its individual components.

Also, you can use documentation or BIOS . Here are all the characteristics of the computer. Using the BIOS, the user can change the value of the delays. This will make your computer run a little faster.

Not all manufacturers of RAM provide this opportunity. Some models may only work with the settings already set. However, if such a function is present, you need to be careful with changing the parameters. Low timings can cause the computer to stop turning on as the operating system fails to boot. This is due to the fact that the RAM will not have enough time to complete the operation.

What to look for when choosing?

The speed of the RAM depends on the speed at which the operation is performed and how much per clock cycle. Therefore, you can not pay attention solely to the latency of the RAM. Also, is not recommended to compare the timings of for different models that operate at different clock speeds.

As an example, consider a DDR3 memory module that operates at a frequency of 1333 MHz. His latency will be 9-9-9-24. The second component has a clock frequency of 2133 MHz, while the timings are 11-11-11-31.

In the first case, the operation execution time will be less than . But this does not mean that the computer will run faster. On the contrary, higher indicators can be observed in the second option. This is due to the clock frequency.