I'm choosing RAM for a PC that will mainly be used for graphic design and video editing, with some light gaming. I understand that lower CAS latency (CL) is generally better, but I'm not sure how important it is or how to compare it with RAM speed. My planned system uses a Ryzen 5 5600, an MSI B550M PRO-VDH WIFI motherboard, an RTX 3060 12GB, and 32GB of DDR4-3600 RAM rated at CL18. Is CL18 too slow, unnecessarily fast, or a sensible choice for this system?
3 Answers
Your selected 32GB DDR4-3600 CL18 kit is a good match for the Ryzen 5 5600 and B550 motherboard. It should work well for design software, video editing, and gaming. CL16 at 3600MHz would be somewhat better, but usually costs enough extra that it isn’t worth it for this build.
CL means CAS latency—the delay, measured in memory clock cycles, before RAM starts returning requested data. You can’t judge it by the CL number alone because RAM speed matters too. DDR4-3600 CL18 has about 10 nanoseconds of first-word latency, which is roughly comparable to DDR4-3200 CL16. A lower-latency kit may perform a little better, but the real-world difference is usually small.
Prioritize compatibility and capacity first, then memory speed, and only after that compare CL ratings. For this system, 32GB is more important than chasing extremely low latency. Make sure the kit is installed as two 16GB sticks and enable the memory’s XMP or equivalent profile in the BIOS so it actually runs at 3600MHz.
That makes sense, thanks for explaining how speed and CL work together.