I'm putting together a PC mainly for graphic design and video editing, with some occasional light gaming. I understand that lower CAS latency (CL) is generally better, but I'm not sure what it actually measures or how important it is compared with RAM speed and compatibility. I'm considering a 32GB (2x16GB) DDR4-3600 CL18 kit for a Ryzen 5 5600, MSI B550M PRO-VDH WIFI motherboard, and RTX 3060. Is CL18 sufficient, or would paying extra for lower latency provide a noticeable improvement?
3 Answers
For your Ryzen 5 5600, motherboard, and use case, 32GB of DDR4-3600 CL18 is a very sensible choice. Compatibility and capacity matter more than chasing the lowest CL number, and 3600 MT/s is a good speed for this platform. CL16 kits may perform a little better, but they often cost noticeably more for a difference you’re unlikely to feel in design work, video editing, or light gaming.
Don’t compare CL18 across different generations without considering the memory speed. CL18 would be slow for some older DDR3 configurations but is perfectly normal for DDR4-3600. Your selected kit should run well with the Ryzen system, assuming the memory is installed as two matching sticks and the motherboard’s memory profile is enabled in the BIOS.
CAS latency is the number of memory clock cycles RAM waits before starting to return requested data. Since faster RAM has shorter clock cycles, the CL number can’t be judged by itself. DDR4-3600 CL18 works out to about 10 nanoseconds of first-word latency, which is roughly the same as DDR4-3200 CL16. A latency calculator can compare different speed and CL combinations, but the real-world differences are usually fairly small.
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