CL16 vs CL18: Which is Faster?

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CL16 is faster than CL18 when all other factors are made equal. But when other aspects of memory specifications are involved, the actual practical result of this comparison can vary greatly. Perhaps a much better thing to ask instead is: CL 16 vs CL18, which is noticeably faster? In this article, we will discuss the differences between CL16 and CL18 memory.

What is CL?

CL stands for CAS (Column Address Strobe) Latency. This is the number of clock cycles (or nanoseconds) needed when a specific string of binary instructions is fed on a column, and when that instruction is available to be used (retrieved).

In layman’s terms, this is how much length of time a RAM stick needs to access information stored on the system’s memory column. Because this is a measurement of delay (how long before something is completed), the lower the CAS latency value, the better.

CL16 vs CL18: Is CL16 Better than CL18?

Pure productivity benchmark statistics dictate that CL16 is better than CL18. However, practically speaking, this value is not really noticeable. Meaning you won’t experience any bumps or dips in performance when using either of the two and so long as both memory kits maintain their stability, the difference is visually indistinguishable.

If product availability (variation) is not an issue, then the default choice would almost always be CL18 kits due to one reason alone: cost. A good number of CL16 kits would always be slightly more expensive than equivalent memory modules with CL18 latency. If you are going to choose the same design or clock frequency anyway, a CL18 stick would most likely allow you to save a bit more, with almost no performance penalties whatsoever.

In case you are adamant about purchasing CL16 modules, then you should at least have a strategic reason to do so. For example, if the price difference is negligible enough that the tiny gains of CL16 kits start making sense. Or, if your system multi-tasks very heavily with lots of medium-level applications running in parallel (therefore warranting every bit of speed advantage it can get). For example, when game streaming.

Video Comparing Cl6 vs CL18

CL Is Not the Only Factor When It Comes to RAM Latency

Because memory clock frequency also matters, which is the actual number of instructions executed per cycle. This is the reason why CAS latency alone should never be considered when purchasing memory kits. Not only do you have to find the lowest CL value available, but you also need to get the highest clock frequency possible.

Nowadays the most common competitively-prized, high-performance CL16 and CL18 kits are available in 3200Mhz and 3600Mhz frequencies. Normally the target should be CL16 and 3600Mhz (XMP default, no tweaks). But due to variations in cost, the most common options usually end up with 3200Mhz CL16 and 3600Mhz CL18. This then brings us to…

3200Mhz CL16 vs 3600Mhz CL18

Long story short, they provide the same latency. 3200Mhz takes a slightly shorter time with CL16 but fewer instructions, while 3600Mhz processes slightly more instructions but takes a bit more time, resulting in a technical draw.

For a more quantitative approach, here’s a formula that we can use to determine the difference in practical latency between the two (measured in nanoseconds):

(CAS Latency/RAM Speed) x 2000 = delay value

(16/3200) x 2000 = 10 nanoseconds

(18/3600) x 2000 = 10 nanoseconds

Same latency, therefore almost the same performance. Any advantages that the higher RAM frequency may have in memory clock-sensitive applications are still effectively made negligible by how small the gap still is between them.

Final Thoughts: Go for The Cheaper Module

In optimizing the specifications of your PC for a certain budget, it is important to always go for tangible gains first, rather than focusing on one or two components alone. In the case of CAS latency values, lower is always (marginally) better. But if the same amount of investment can produce a bigger impact on another specification, such as RAM capacity, then the small gains from getting a CL16 kit will always be worth sacrificing.

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