Understanding Memory on AMD’s Zen 2 Architecture: What’s the “Sweet Spot” for Ryzen 3000XT CPUs?
Before we discuss what sort of memory you should aim for in a Zen 2 system with CPUs like the new Ryzen 5 3600XT, Ryzen 7 3800XT, or Ryzen 9 3900XT, let’s first examine the current landscape of PC hardware: what do we have access to right now, and how do these technologies work? Currently, AMD provides the best technology overall in the consumer desktop market with their Zen 2 CPUs which support PCIe 4.0 by utilizing their proprietary Infinity Fabric interconnect architecture. Infinity Fabric is the foundation upon which AMD has built each of its Zen architectures, and the dramatic success they’ve had thus far could potentially see them extend this paradigm to Big Navi. While the speed of system memory is a critical function for it, we’re going to start by detailing the concepts behind the Infinity Fabric.
What Exactly is Infinity Fabric?
Per the above block diagram, where PCIe (peripheral component interconnect express) is responsible for the communication between your CPU, chipset, and the various accelerators, slots, and ports on your motherboard, AMD’s Infinity Fabric functions much the same between separate integrated circuits within their processors. What’s most intriguing is the fact that Infinity Fabric is not only able to link separate die chiplets on the same package, but it can also bridge multiple packaged chips between sockets. What’s even cooler than that is it looks like we’ll eventually see Infinity Fabric extend beyond the bounds of the motherboard socket to provide a unified interconnect protocol for CPUs and GPUs. The potential performance of a system with shared memory between the CPU and GPU is, quite honestly, exhilarating.
Infinity Fabric splits into Scalable Control and Scalable Data Fabrics (SCF and SDF). The Control Fabric plane handles power management, security, and general chip operations in the SCF plane. By contrast, the Data Fabric plane is responsible for the data link between Core Complexes (CCXs) on multi-chip-module (MCM) CPUs, like many in Zen 2, and all input/output (I/O), both of which the SDF plane bridges to system memory. Below are two block diagrams to illustrate this dynamic, one indicative of Ryzen/Threadripper consumer desktop CPUs, another of EPYC enterprise server CPUs.
The CCXs transmit data between each other with a Cache-Coherent Master (CCM) and between discrete components with an I/O Master/Slave (IOMS), which are the only two interfaces able to send and receive DRAM requests from the Universal Memory Controller (UMC). That process on the Data Fabric then comes together with the Control Fabric thanks to Infinity Fabric On-Package and InterSocket (IFOP/IFIS) serial/deserializer (SerDes) links. These SerDes blocks allow for data conversion from serial to parallel, and vice versa, and transfer it between CCXs on the same chip and between chips installed on a dual-socket motherboard. It is this multiprocessing capability that’s eventually going to be expanded to GPUs as Infinity Fabric continues to grow into an almost entirely unified interconnect protocol.
The final key component is CAKE, and while it’s not the delicious kind, this CAKE brings Infinity Fabric together with the assistance of (de)multiplexers (DEMUXs/MUXs). The Coherent AMD SocKet Extender module: CAKE, encodes/decodes SerDes information and sends/receives it over not just IFOP and IFIS, but any SerDes interface, i.e., PCIe, SATA, USB, and IP. Multiplexers and demultiplexers make everything possible by switching multiple inputs through one output, or by switching one input between several outputs, respectively. Thus, CAKE and DEMUXs/MUXs are how Infinity Fabric can scale so drastically and communicate with nearly all other existing data busses.
Now, why does any of this matter? Because the performance of Infinity Fabric ties directly to memory performance, and the recently launched Matisse Refresh Ryzen 3000XT CPUs are extremely mature versions of the Zen 2 architecture that should have significantly improved overclocking potential. If IFOP operates at four transfers per CAKE clock, and IFIS operates at eight transfers per CAKE clock, and the CAKE module is typically clocked to a 1:1 ratio with memory frequency then…
How Does Memory Affect Performance?
On Zen 2, it is possible to overclock your Memory Clock (MEMCLK), and Fabric Clock (FCLK) speeds independently from one another. Further, the Memory Controller Clock (UCLK) speed can have either a 1:1 or 1:2 ratio with your MEMCLK (UCLK:MEMCLK). These settings, in addition to your CAS latency timings, all significantly impact Zen 2 system performance across both production and gaming workloads. You’ll see benefits like higher FPS in most games, faster storage transfer speeds, and shorter completion times in workstation programs.
That said, it’s important to note that most platforms, even the most expensive enthusiast-class motherboards, tend to hit a wall anywhere between 1800-2000MHz FCLK, which is when you start running into stability issues. It’s relatively rare for people to achieve a stable 1900MHz+ FCLK, so always remember, you’re not just playing the silicon lottery with your CPU, but with virtually every PC component in your system, including the motherboard itself. Although, that might be liable to change as more builders scoop up the new 3000XT CPUs and begin testing things like how much more memory overclocking headroom we might have now.
So What Memory is Best for Zen 2?
Generally, the best and most stable configuration overall seems to be UCLK=FCLK=MEMCLK; somewhere at or below 1800MHz; with the best CAS Latency you can afford or that you can manage in the BIOS. For example, 1800MHz:1800MHz:1800MHz at CL 14-16-16-36. Keep in mind; your MEMCLK here would actually translate to 3600MT/s as it is DDR4 or Double Data Rate 4 memory, and lower CAS Latencies determine the faster speed between two memory kits with identical frequencies.
Now, as for the best memory for Zen 2? That largely depends on your use case. Are you interested in taking the time to tweak and benchmark your memory configuration in the BIOS to try and get the fastest clock speeds, tightest timings, and lowest latency possible? Or are you looking to plug, play, set, and forget?
For the more confident overclockers out there, you must also consider your budget, because when you start looking at DDR4 kits faster than ~3600MHz CL14 and larger than 16GB, prices begin rising sharply. Other important factors include the amount of RAM you need, and what CPU you’ve decided to purchase. Memory starts to get even more expensive beyond 32GB. However, you might be able to get away with a slower kit and try to overclock it if you’re looking at picking up one of the new Ryzen 3000XT CPUs that just launched. Regardless, for any Zen 2 machine, the fastest and most stable memory speeds with the best price-to-performance value overall sit, generally, between 3200-3800MHz at CL14. Most options in that range offer the flexibility for almost any capacity with the potential to overclock manually in place of default XMP profiles.
Best RAM for Ryzen 3600XT, 3800XT & 3900XT – Our Recommendations
|Award||Memory Kit||Design||CAS Latency||Current Price|
|Best RAM for Entry-Level Ryzen Matisse Builds||16GB (2 x 8GB) G.Skill Flare X DDR4-3200||14-14-14-34||$110|
|Best RAM for Ryzen Matisse Gaming Builds||16GB (2 x 8GB) G.Skill Trident Z Neo DDR4-3800||14-16-16-36||$289|
|Best RAM for Ryzen Matisse Mixed-Use Builds||32GB (2 x 16GB) G.Skill Trident Z Neo DDR4-3200||14-14-14-34||$293|
|Best RAM for Ryzen Matisse Workstation Builds||64GB (4 x 16GB) G.Skill Trident Z DDR4-3200||14-14-14-34||$589|
|Best RAM for Threadripper Zen 2 Builds||128GB (8 x 16GB) G.Skill T rident Z Royal DDR4-3200||14-14-14-34||$1586|
Best RAM for Entry-Level Zen 2 Builds
AMD has a vast array of Zen 2 processors available from $100 up to $4000, and they each perform exceptionally well. Thanks to this exceptional range of price-to-performance in the CPU market, we see the same value and quality on offer for other components as well, like with the 16GB (2 x 8GB) G.Skill Flare X DDR4-3200 memory kit. The maximum advertised speed supported for Zen 2, across the board, is only 3200MHz, but if you’re itching to overclock any Ryzen 3000X or 3000XT CPU, the rated 14 CAS Latency here will easily allow you to do so. The default XMP profile for this kit is more than enough for fantastic performance during everyday use, and for $110 G.Skill arguably has the best option on the market for anyone looking for a standard 16GB of total memory while still having the opportunity to upgrade with 2nd kit later on.
Best RAM for Ryzen Matisse Gaming Builds
Let’s say you’ve set your sights on a processor like the Ryzen 5 3600XT, and you want a no-compromises build for the ultimate FPS performance. In that case, you’re going to want to go with a 16GB (2 x 8GB) G.Skill Trident Z Neo DDR4-3800 memory kit. Not only do you end up right in the “sweet spot” for memory speed on Zen 2, but you’ll have that speed along with 14-16-16-36 CL timings out of the box with XMP! Provided your CPU/motherboard combo is capable, you should be able to push a pretty drastic memory configuration in your BIOS with this kit if you’re interested. Another benefit with this particular set is you’ll have the option to upgrade to 32GB total memory with a 2nd kit if you start finding yourself spending more time in productivity workloads and need the extra capacity!
Best RAM for Mixed-Use Ryzen Matisse Builds
For builders who already know, they’re going to be doing an even split of gaming and photo/video editing, rendering, code compilation, or otherwise, we suggest the 32GB (2 x 16GB) G.Skill Trident Z Neo DDR4-3200 memory kit. Here you’ll start with a sufficient amount of RAM to leverage as much productivity performance as possible while having more than enough for general use, gaming, and extreme multitasking across multiple displays. Out of the box, you meet the maximum advertised speeds supported by Zen 2 processors and 14-14-14-34 CL timings with the default XMP profile. This RAM is an excellent choice if you’ve decided to build around a Ryzen 7 3800XT, and should result in a powerful combination that allows you to tackle anything you can throw at your machine. Finally, if your mixed-use ends up developing into more focused productivity work, you’re able to move up to 64GB total memory with a 2nd kit. At PremiumBuilds, we always factor in as many of our builders’ potential needs as possible. We understand the fact that those needs might change because people change and grow over time, hence our focus on leaving an upgrade path as often as possible in all of our recommendations and build guides.
Best RAM for Workstation Ryzen Matisse Builds
You’re pretty much decided on at least a Ryzen 9 3900XT at this stage. You already know you’re building a high-end workstation and want uncompromising performance with enough capacity to leverage as much of your productivity programs as possible. If that’s the case? Look no further than a set of 64GB (4 x 16GB) Trident Z DDR4-3200 memory. No fluff, no wacky designs, no RGB lighting, just beefy heat spreaders, and the highest advertised speed, and lowest CAS Latency, with the default XMP profile. If you need a higher frequency, your default timings are 14-14-14-34, which is more than enough room to play with faster clocks. Daily use and FPS performance are just icing on the cake here too, as 64GB is more than you’ll ever need for anything outside of workstation tasks for the foreseeable future.
Best RAM for Threadripper Zen 2 Builds
If you’ve got deep pockets and a burning desire for the most incredible consumer desktop CPUs ever released, to date, then you’re going to want a set of 128GB (8 x 16GB) G.Skill Trident Z Royal DDR4-3200 memory. Even with the cheapest Ryzen Threadripper 3960X costing over $1300, there’s no room for the word “budget” for a system with 24 cores, at minimum. Your motherboard alone is going to run you at least $325 nowadays, and if you want a Threadripper as your CPU, you’re likely interested in the best possible options for all of your hardware. With the Trident Z Royal kit, you’re filling out every DIMM slot with the highest advertised speed, 14-14-14-34 CL timings, and you still have room to overclock it from there. The diamond-esque RGB lighting and rose gold finish on the heat spreaders might be a bit much, but honestly, what isn’t when it comes to Threadripper?
When it comes to the best memory performance at every price bracket, G.Skill dominates the market with a shocking number of CL14 kits in nearly every relevant size combination. Opting for the lowest CAS Latency possible not only offers similar performance to higher frequency kits with worse timings but also allows you to loosen your timings up for even better MEMCLKs. Specifically, the G.Skill Trident variants like the Z, Z Neo, and Z Royal consistently provide the best options for stellar XMP profiles out of the box while also leaving prospective overclockers the opportunity to squeeze higher speeds out of them by loosening the timings a little bit. Either way, you end up in the ideal range for peak system performance on most Zen 2 processors like the new Ryzen 3000XT chips. Whether you’re interested in extreme memory overclocking, or you’re only worried about diving into your favorite desktop programs ASAP, we’re confident you’ll be thrilled with any of our picks today!
Are you excited about the potential of AMD’s Infinity Fabric and what it could mean for the future of PC performance? Do you feel you have a better understanding of how things like memory performance affect Zen 2, or how the Infinity Fabric interconnect architecture works? Are you planning on upgrading to a new Ryzen 3000XT CPU? Let us know in the comments below and, as always, thanks for reading!