Introduction
I have recently gotten a common question about memory speeds from several people who were planning on building new AMD Ryzen desktop systems. The question is, what speed RAM do you need for a Zen 2 CPU?
It is easy to become confused about this if you look at the published memory specifications for many newer motherboard models. The Gigabyte B550 AORUS MASTER shown below is a prime example. It says that 3rd Gen AND Ryzen processors (Zen 2, Ryzen 3000 series) can support DDR4-5200 (O.C.) RAM.
Does that mean you need to go out and buy DDR4-5200 RAM? Personally, I don’t think so, but I can see why people might assume that is necessary. If you look at the Qualified Vendor’s List (QVL) for your motherboard, you can see all of the different memory modules that the motherboard vendor has actually tested on that motherboard. The first page of the Memory QVL for the Gigabyte B550 AORUS MASTER is shown below.
The top four rows in the QVL show the same 16GB Crucial Ballistix Max BLM8G51C19U4B memory kit (which costs $899.99 for two 8GB DIMMs). This absolutely not what you want for normal usage!
It is extremely expensive (about 10X what “normal” RAM costs) and it is only supported in two memory slots at this speed. Using 8GB DIMMs in a new build is also not what you typically want to do. Depending on your budget, 16GB or even 32GB DIMMs are a better choice. That Crucial memory kit certainly is pretty though!
Faster Must Be Better, Right?
Not in this case, at least once you go above a certain memory speed with Zen 2. As the AMD slide below shows, once you go above DDR4-3733, the Infinity Fabric switches from a 1:1 ratio with the memory clock to a 2:1 ratio. In order to support DDR4 above 3733, the chip will automatically change the memory controller to Infinity Fabric clock ratio from being 1:1 to 2:1, and the memory latency will increase.
What Speed RAM Do You Need For a Zen 2 CPU?
The general consensus seems to be that DDR4-3600 CL16 or DDR4-3200 CL14 is the sweet spot. There is usually not much performance or price difference between those two.
No matter what RAM you get, make sure (at a bare minimum) that you go into the BIOS and enable XMP. Otherwise, your RAM will be running at the default JEDEC speed of something like 2133MHz. I talk more about this here. If you want to go further, you can try using the DRAM Calculator for Ryzen.
Here are some good YouTube videos on this subject.
- AMD Ryzen 3000 Memory Benchmark & Common RAM Mistakes (fClock, uClock, & mClock)
- How to Manually Tune Your DDR4 Memory For Ryzen
- Watch this BEFORE buying an AMD CPU! – Every RAM Speed Tested
What About Ryzen 5000 Processors?
The image below is supposedly a leaked slide from an upcoming AMD presentation that purports to show that the sweet spot for AMD Ryzen 5000 series processors will be DDR-4000. I have some doubts about the authenticity of this slide, but I thought it was interesting.
Final Words
The main point here is that you don’t need to buy very expensive DDR4 RAM above DDR4-3600 for a Zen 2 processor for most normal usage. Please don’t waste your money on needlessly expensive RAM!
If you have any questions about this post, please ask me here in the comments or on Twitter. I am pretty active on Twitter as GlennAlanBerry. Thanks for reading!
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