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Home / Peripherals / CL18 vs. CL16: Which RAM Is Better?

CL18 vs. CL16: Which RAM Is Better?

Every gamer with a serious passion for high performance, seamless gameplay, and low latency is constantly searching for a way to upgrade their PC. Whether that be through a new processor, graphics card, or RAM setup, it pays off to know what gets you the highest speeds before you make a purchase.

CL16 is better than CL18 because it has a lower CAS latency, which means it takes fewer cycles to process demands from your CPU and make that data available. CL16 will give gamers a faster response time than CL18 RAM with the same memory speed because it takes only 16 cycles to process data, whereas CL18 would take 18 cycles.

However, the difference is negligible to many with untrained eyes. The main factor that dictates how visible the difference depends on whether or not you have a Ryzen CPU or not. So, how do you decide which one you need?

In this article, I’ll discuss CL in detail, the difference between CAS latency and RAM speed, and how that affects gamers with different CPU brands. Let’s get into it.

What Does CL Mean?

CL stands for CAS Latency, or Column Access Strobe Latency, and represents how fast your RAM can process commands from your processor and prepare the necessary data. In general, a lower CAS latency means faster performance.

If you compare a CL16 3200 MHz RAM with a CL18 3600 MHz RAM, you’ll find that even though the CL18 has a higher memory speed, the CL16 will still perform faster, and that performance gets quicker the higher the memory speed gets. This is because memory speed and CAS latency are two different things.

CAS Latency

CAS Latency is a measurement of how many clock cycles it takes your RAM to process a command from your processor. Lower CAS latency means faster performance, regardless of the memory speed (assuming there isn’t a gap of more than 1,000Hz between the CL16 and CL18).

Gamers who want to minimize latency with their RAM should choose a CL16 over a CL18 because it will perform faster than a CL18 in every way that is relevant to gamers.

CAS Latency 3200 MHz vs. 3600 MHz

Looking at 3200 MHz RAM versus 3600 MHz RAM, you see that the average 3200 MHz RAM has a CL range of 14-16, whereas a 3600 MHz RAM has a CL range of 15-19. The latter has a wider range but, ultimately, the former’s range has a lower minimum. This means that a CL14 3200 MHz RAM will perform faster than a CL18 3600 MHz RAM, despite its higher memory speed.

This holds true for a CL16 3200 MHz RAM compared to a CL18 3600 MHz RAM, but the difference is less noticeable here. The average gamer will hardly be able to notice the difference between the two (roughly 5%), so most people tend to disregard the CL and opt for higher memory speeds without knowing what they’re missing.

However, if your end goal is to maximize your computer’s performance, you want the lowest possible CAS latency. To find the CAS latency of your RAM, you can either check the manufacturer’s website or by examining your RAM stick. You’ll see a series of 3 or 4 numbers on the stick; the first one is CAS latency.

RAM Latency

RAM latency is separate from CAS latency, but provides less of an effect on your RAM’s performance speed than you’d think. RAM latency represents the time delay for the memory to complete a clock cycle per second.

RAM latency is calculated by dividing the memory speed by the CAS latency and is measured in nanoseconds. For a frame of reference, let’s compare the RAM latency of a CL16 3200 MHz RAM and a CL18 3600 MHz RAM.

CL16 3200 MHz RAM has a RAM latency of 10 nanoseconds, which means each clock cycle takes 10 nanoseconds to complete. With a CL16, your RAM needs to complete 16 clock cycles for each stream of data to be received and processed. Put simply, a command will take 160 nanoseconds to go from input to output.

CL18 3600 MHz RAM also has a RAM latency of 10 nanoseconds, but with a CL18, it needs 18 clock cycles to get from input to output. This places the total process time at 180 nanoseconds, a 12% increase in duration from CL16 3200 MHz.

So, even with a higher memory speed, a CL16 can outperform a CL18 in most regards.

RAM Speed vs. RAM Latency

So, what’s the difference between a RAM’s speed and its latency?

RAM speed is measured in megahertz, most often referred to as “MHz”. It’s a measurement of a RAM’s clock speed, which dictates how many times per second the RAM can access its memory.

This translates to a 3200 MHz RAM being able to access its memory 3200 times per second, and a 3600 MHz RAM can access its memory 3600 times per second. The higher the memory speed, the better it contributes to the RAM’s performance.

RAM latency, as described above, is how long of a delay the memory needs to complete a clock cycle, which is informed by the RAM speed. With higher RAM speeds, you get lower RAM latency, which means you get faster performance.

How CAS Latency Plays Into RAM Speed and Latency

Now that you have an understanding of the three main components that dictate RAM performance, you can learn how they affect each other.

First, higher RAM speeds equate to lower RAM latency, which means your RAM can access its memory more times per second with less delay between cycles.

Here is where different CAS Latency specifications come into play. With a lower CL rating, your RAM can complete the command with fewer cycles than higher CL ratings. Let’s look at it using 3200 MHz and 3600 MHz RAM as references again.

CL16 vs. CL18 3200 MHz

At this memory speed, a CL16 will perform much faster than a CL18. The RAM can access its memory 3200 times per second, with a similar latency between CL16 and CL18, with CL18 being a little slower. So, with a CL16 RAM, you can process data faster because it takes two fewer cycles than a CL18 to get the job done, and there’s less RAM latency.

CL16 vs. CL18 3600 MHz

The same holds true here. CL16 has about half a nanosecond less RAM latency than the CL18. This means that while they can both access memory 3600 times per second, there is a slightly longer delay with CL18 in the access cycle than the CL16.

The difference between the two would be less noticeable than comparing them at 3200 MHz because there is a slightly wider margin.

How Different CPUs Affect RAM Performance

AMD CPUs

AMD, kings of proprietary computer technology, produces Ryzen CPUs designed with an infinity fabric core system, also known as IF. The IF system has its own clock time features, called FCLK, and is limited to roughly 2000 MHz clock speeds.

So, if you have a Ryzen CPU, you can disregard clock speed for the most part and prioritize a lower CL. This way, you can get the most out of Ryzen’s tight clock cycles by reducing the number of cycles necessary to process a command.

Intel CPUs

You’ll want to do the opposite if you’re using an Intel CPU. Intel doesn’t integrate such tight clock cycles into their processors, so you would get the most out of your processor with a higher memory speed.

With a higher memory speed and CL, you can overclock the CL from 18 to 16, which gives you faster performance than a high memory speed would get on a Ryzen with CL18.

Our Final Take

For most purposes, a CL16 will outperform a CL18 in nearly every way. It requires fewer cycles to process a command, regardless of what the actual memory speed is. The only time when a CL18 might perform better is if you’re on an Intel CPU, and even then, you’ll need to overclock the RAM to get it as fast as the CL16.

FAQs

Is Higher CL Better?

No, a higher CL makes your RAM perform slower. To maximize your RAM’s performance speed, get a lower CL. The performance increase is worth the price increase for serious gamers with an eye for smooth gameplay.

How Do I Know if My RAM is CL?

All RAM have a CAS latency, but sometimes the information is displayed in different locations. Generally, you can find it printed directly onto your stick with a series of numbers, the CL being the first in the series. If it’s scratched off or you’re having trouble locating it, check your manufacturer’s site.

Can You Mix RAM With Different CL?

As with RAM storage capacities, you should make sure your RAM sticks have the same CAS latency for maximum performance. When you have two RAM sticks with different CLs, it causes a delay in the processing of your computer.

About Isaac Atia

Isaac AtiaAs an avid gamer for 20+ years, I spend hours researching custom PC builds and parts. I review various CPUs, motherboards, RAM, and gaming peripherals. I often test parts in my home office in New York City. To ensure the highest level of accuracy, I often consult with other experts and industry professionals.

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