CL stands for “CAS (Column Access Strobe) Latency” and is one factor that differs between different RAM sticks.
In short, CAS Latency determines how quickly your RAM can process and prepare data when ordered by the CPU. Let’s take an in-depth look at CAS Latency and how it affects your computing experience.
CAS Latency: An In-Depth Explanation
CAS Latency is measured in clock cycles.
When using Asynchronous DRAM, the delay is measured in nanoseconds. Synchronous DRAM typically uses clock cycles to measure the delay. A clock cycle is the measure of time used to track the delay between an order from the CPU to retrieve information from the memory column.
Typically CAS Latency will be denoted on the memory somewhere with a measure of CAS (number) or CL (number). Still, the timing doesn’t have a fully standardized measurement label.
So, ensure the RAM you’re buying has the CAS Latency you’re looking for. With CAS Latency, you’re typically looking for a lower number—thus a lower latency—rather than a high number. So CL 16 RAM will be a faster unit than CL 18 RAM.
Simply put, the CAS Latency is how long it takes for the RAM unit to access its memory column and make that information available to the RAM output and, thus, the computer controller or CPU.
CL 16 vs CL 18: What’s the Difference?
As we’ve mentioned, CL 16 RAM has a lower latency than CL 18 RAM.
However, that is the only notable difference on this axis. RAM sticks are measured on multiple axes that, together, provide a comprehensive view of what to expect from an individual RAM stick.
Many people confuse CAS Latency with Data Transfer Speed regarding RAM. However, these metrics are mainly independent, even if they work together in the overall RAM ecosystem. Therefore, to get a full view of what to expect from your RAM sticks, you’ll need to look at all the metrics and see how they interact.
CL 16 vs CL 18: How Do They Affect RAM Speed?
When looking at metrics regarding RAM speed, the two factors you want to look at most closely are the clock speed and the CAS Latency. Together, these two factors determine how quickly your RAM can read and write data.
If two RAM kits have the same clock speed, you’ll want to choose the kit with a lower CAS Latency. A faster CAS Latency will give you more speed in a set of kits with the same clock speed.
However, it’s not quite as simple if you’re looking at RAM kits with different clock speeds. Additionally, some units use a Latency Range. This feature allows the RAM sticks to adjust their latency speed based on the task they’re performing.
A CAS Latency Range of 14–16 is typical for RAM running at a clock speed of 3200 MHz. On the other hand, RAM with a clock speed of 3600 MHz typically features a CAS Latency Range of 15–19.
However, due to the functional speed boost achieved with a lower CAS Latency Range, the 3200 MHz/CL 14–16 RAM will outperform the 3600 MHz/CL 15–19 RAM.
Essentially, even though the 3600 MHz RAM transfers more data per clock cycle since the CL 14–16 RAM can retrieve data in upwards of three fewer clock cycles, it outperforms the CL 15–19 RAM in practice.
However, if both RAM kits have the same clock speed, CL 16 RAM will always surpass CL 18 RAM, even if only marginally.
CL 16 vs CL 18: RAM Latency
RAM latency is the overall speed at which your RAM can read and write, the speed it takes to complete one clock cycle.
While it may sound like it’s the same as your RAM speed, RAM latency has more factors than the raw speed of the RAM. For example, CAS Latency does affect overall RAM latency. So, you can’t forego this factor if you’re looking for the smoothest performance.
RAM Latency is typically measured in sequential numbers such as 6-8-8-22, which tell you how quickly your RAM can perform specific tasks. Unfortunately, the exact metrics and how they come to those conclusions are rather intricate and require much intimate knowledge of computer hardware. So, we won’t go too in-depth on how it works.
Instead, it would be best to look for a combination of high data transfer rates and low CAS latency to give your computer the best overall performance.
CL 16 vs CL 18: CPU Interfacing
Finally, you’ll want to check what kind of CPU you’re using to ensure perfect integration of your RAM into your computer ecosystem. The two major CPU manufacturers, AMD and Intel, interface with your RAM uniquely.
This uniqueness means that you’ll want to choose your RAM and CPU with the intention of them working together as a unified ecosystem rather than two separate components.
Ryzen CPUs tend to be slightly nicer to your RAM than Intel CPUs. This differential is because Ryzen CPUs generally have faster memory speeds than their Intel counterparts.
This slight difference means that Ryzen CPUs can better use RAM sticks with a lower CAS Latency.
Ryzen CPUs are also unique in that they have unique clock time characteristics for the CPU cores and Ryzen CPU chips. The whole system ecosystem has a unique clock time as well.
These clock speeds are generally limited to around 1800 MHz–2000 MHz. The system functions most optimally when its RAM clock rate is around 2× the rate of the system clock rate.
Focusing on your RAM’s clock speed is unnecessary when you have a Ryzen CPU.
Instead, it would be most helpful if you ideally concentrate on getting the lowest possible CL RAM within your price range. Getting low-latency RAM will make the best use of the Ryzen chipset’s tight clock cycles.
Intel CPUs are the polar opposite of AMD CPUs regarding RAM interfacing.
Unlike AMD, Intel CPUs don’t run at a tight clock speed. So, the data transfer rate is king with Intel CPUs. On the other hand, low-latency RAM typically comes at a lower data transfer rate.
So, if you’re looking to get the most out of your build—really milk every component for what it’s worth—you’ll want to buy 3600 MHz/CL 18 RAM and modify the RAM to run at a rate of CL 16.
With an Intel CPU, you’ll lose a lot of power and speed by “upgrading” to 3200 MHz/CL 16. To get the best of both worlds, you need to get under the hood and overclock your RAM to match the system build of your CPU.
If modifying your RAM is out of the question (a valid choice!), 3600 MHz/CL 18 RAM is more appropriate for an Intel build.
Will I Notice a Difference Between CL 16 and CL 18 RAM?
The truth is that unless you’re doing very intensive tasks like gaming, video editing, graphic design, or programming, you probably won’t see much difference between CL 16 and CL 18 RAM.
On average, CL 16 RAM is only about 1% faster than CL 18 RAM when used in ideal conditions.
So, suppose you’re looking at a hefty price tag. In that case, you might consider downgrading your RAM to CL 18 to offset some of the other more expensive components.
Understanding the inner workings of your computer is the first step to getting the most out of it.
RAM is just one component, but understanding the CAS Latency and how that affects your overall computing experience will help you get the most out of your computer and utilize your resources most effectively.