We’ve had a few days with our Zen 3 Ryzen 5800X and the bulk of that time has been spent investigating the impact of RAM speed on this new architecture. Since its inception, the Zen design has shown impressive performance scaling with RAM Speed. This a function of the design of the CPU itself.
In short, the CPU cores are connected to the rest of the PC via an interconnect chip known as ‘infinity fabric’. The speed this chip is running at is instrumental to the overall performance of the CPU. Luckily, AMD has an open attitude towards allowing users to tweak settings to their heart’s content, so all of this is adjustable in BIOS. The optimum settings involve ensuring that the RAM speed matches the Infinity fabric frequency 1:1. With these two clock speeds in sync, memory access latency is reduced and you enjoy a performance boost.
Previous Zen 2 RAM Investigation Summary – will Zen 3 continue the trend?
In our previous Zen 2 Ram Speed article we demonstrated the clear performance benefits of increased RAM speed with optimum performance at 3600 and 3733Mhz, and infinity fabric at 1800 and 1866Mhz respectively (note that DDR ram being Double Data Rate, it reports speeds at twice the actual clock frequency). Once you exceeded the ability of the Infinity fabric to match RAM speeds 1:1 however things broke down with increased latency costing performance despite the improved speeds.
The benchmark tests that showed clearest scaling were 3DMark Timespy, and Shadow of the Tomb Raider. Rainbow 6 Siege’s FPS also showed strong correlation with RAM speed.
RAM Speed Scaling on a Zen 2 CPU, the Ryzen 3600.
In this investigation we focussed on the following questions:
- Firstly, does Zen 3 improve our ability to lift Infinity Fabric speeds to match faster RAM?
- Secondly, does Zen 3 performance scale with RAM speed in the same way we’ve become accustomed to?
- Finally, can we use this information to make any recommendations about the best RAM for your Zen 3 system?
Overclocking RAM on Zen 3
Overclocking on the Zen 3 platform proved relatively straight forward. Using our Patriot Viper 4400Mhz memory kit, which comprises Samsung B-Die Ram with CL19 timings, we were quickly able to establish that our Ryzen 5800X was stable at 4000MHz with Infinity Fabric (Fclck) at 2000MHz. 4066MHz was not stable. We were able to tighten timings down to CL 16-16-16-34 at 4000MHz. From there we established representative RAM profiles across a spectrum of speeds to emulate widely available RAM kits.
Zen 3 RAM Synthetic Test results: CineBench R20 and Timespy
Honing in on the benchmarks that matter we again showed that Cinebench is not a reliable indicator of performance linked to RAM: Our scores varied little with RAM speed.
Note that the scale starts at 5000 Points: The difference between these results is small enough not to cause concern, and it’s not possible to consider this a ‘trend’ in performance owing to the marginally lower scores at higher speeds. Cinebench R20 appears almost oblivious to the RAM speed of the System with even 2133MHz not causing a significant performance deficit.
TImespy is a Dx12 based benchmark with a portion dedicated to CPU performance in isolation. It’s those scores we’re concentrating on here.
In Zen 2 we saw a strong positive trend with RAM speed from 2133MHz to 3733MHz, and we observe the same here on Zen 3: Slower RAM is a serious detriment to performance, with 3600MHz yielding much higher results. However, increasing speeds into the realms of 3800 and 4000MHz sees little if any improvement in performance with 4000MHz CL18 close but slightly behind 3600MHz and 3800MHz. Tightening timings to CL16 sees performance slacken to just under 12000 points: A very interesting results given what we thought we knew about infinity fabrics speed and its relationship to CPU performance. We don’t know the reason for this given that all things being equal these tighter timings should increase performance, or at the very least not harm it.
Moving onto key gaming benchmarks, we looked at Rainbow 6 Siege and Shadow of the Tomb Raider. Both of these titles demonstrated the benefits of faster RAM on Zen2 and again showed the negative impact once the 1:1 infinity fabric to memory clock ratio was broken.
Zen 3 RAM Gaming Benchmarks: RAM Speed vs FPS
1. Rainbow 6 Siege
Here we again see the same performance scaling to 3800MHz, followed by a slight tailing off as RAM speed climbs higher. Tightening timings at 4000MHz helps a little. Despite maintaining a 1:1 infinity fabric ratio throughout, we’re seeing a similar but less pronounced softening of performance past 3800Mhz just as we did on Zen 2.
2. Shadow of the Tomb Raider
This game again uses DX12 and has a comprehensive benchmarking tool which gives us interesting insight into the factors affecting the game’s performance. Specifically, it breaks down performance into ‘CPU game’ and ‘CPU render’ as well as GPU performance and indicates how GPU limited the benchmark is. All tests were conducted at 1080p medium on a GTX 1080 Ti but even that induced a GPU limitation due to the prodigious speed of the Ryzen 5800X. Due to the benchmark independently reporting CPU frame rates it can be eliminated as a factor.
We once again see a similar trend here with peak performance at 3800Mhz, and then a slackening at 3933Mhz and 4000MHz. From 3600-4000Mhz performance is in the same ballpark with variances that aren’t going to be material in the real world. Note that none of these will impact gaming at normal settings: You will be GPU limited at FPS below these numbers in this detailed AAA title.
Conclusion: 3600MHz is still the best RAM for AMD’s Ryzen CPUs
We can now set about answering the questions we posed at the outset:
Zen 3 does allow us significantly higher Infinity Fabric clocks, and with it higher viable memory overclocks. This is exciting for overclockers because of the potential performance gains it brings.
However moving on to the second question, we do not see straight forward linear scaling until the break down of infinity Fabric Clocks as we did with Zen 2: In this instance, performance tails off even with a 1:1 infinity fabric ratio despite faster ram with tighter timings and lower latencies. In the real world, these slight variances won’t be noticeable, but similarly, we are not seeing anything like the scaling from 3600MHz-4000MHz as we get from raising Ram speeds from 3200MHz – 3600MHz.
Finally, we can now make confident recommendations on the basis of these results, which are in line with those obtained by experienced overclockers: 3600MHz RAM is still the best option for Ryzen CPUs. To arrive at this conclusion we can consider firstly that performance plateaus or even tails off after that. Secondly, there is the cost and availability of RAM. Since 3600MHz became the ‘sweet spot’ for Zen 2 Manufacturers have produced a number of fantastic RAM kits and prices have dropped due to a glut of RAM supply. To obtain RAM significantly faster than 3600MHZ prices jump from around $80/16GB for 3600MHz CL16, to $100 or more for 4000MHZ CL18 which as our investigation above shows will be marginally slower on Zen 3. Finally, investigations by Gamers Nexus indicate that dual-rank DIMMs may be slightly faster, making a 32GB kit in 2x16GB Configuration at 3600MHz likely to be ideal for most people.
With all of this in mind, we make the following recommendations for RAM for Zen 3 builds in 2021:
RAM Recommendations for Zen 3 Builds
| Award | Design | Model |
|---|---|---|
| Best All-round RAM Kit for Zen 3 Builds |  | G.Skill Ripjaws V 32GB DDR4-3600 CL16 |
| Best RAM for Zen 3 Gaming Builds |  | Crucial Ballistix 16GB DDR4-3600 CL16 |
| Best Enthusiast RAM Kit for Ryzen Zen 3 | | G.Skill Ripjaws V 16GB DDR4-4000 CL16 |
| Best RGB RAM for Ryzen Zen 3 |  | G.Skill Trident Z Neo DDR4-3600 CL18 |
| Best 64 GB RAM Kit for Ryzen Zen 3 |  | Corsair Vengeance LPX 2x32GB DDR4-3200 CL16 |
Best All-round RAM Kit for Zen 3
Combining all that we have learnt so far about Zen 3 Memory performance, the G.Skill Ripjaws V 32GB DDR4-3600 CL16 kit hits all the bases. Using 2 dual-rank 16Gb Sticks with 3600MHz frequency and tight 16-19-19-39 timings mean you’ll be as close to optimized as one click can get you just by enabling the A-XMP profile. 32GB RAM provides ample for productivity, the most demanding games and light creative work such as video editing. At $150 it’s reasonably priced for 32Gb, exactly double the cost of the 16Gb equivalent. This is the RAM kit we’re confident meets the needs of almost everyone looking to take advantage of the prodigious power of the Zen 3 CPUs for gaming and general use.
Best RAM for Zen 3 Gaming Builds
Crucial is Microns commercial brand and the Ballistix 16GB DDR4-3600 CL16 kit uses Micron E-Die RAM chips to deliver the performance sweet spot at a very attractive price. 16GB is still ample for almost all games and general use and multitasking. It’s been available for some time at the $75 price point making it a very worthwhile purchase and the best value of all the popular 16GB kits. The 3600MHz speed enjoys widespread compatibility with Zen 3 CPUs, whilst the quality of the E-Die chips lend themselves to tweaking and overclocking for even more performance if the mood takes you. If not the embedded A-XMP profile will ensure reliability and stability at the rated speeds. It is a 2x8GB stick for dual channel operation and any RAM kit you consider should be a dual-stick kit because of the large performance benefit that brings. The kit ships with discreet black anodized heat spreaders that integrates well with most builds but it is also available in white or red if that better suits your preferences. With this kit just $10 more than the most basic of RAM kits from less well-established brands we see no reason to opt for anything else.
Best Enthusiast RAM Kit for Ryzen Zen 3
If you want to explore the limits of memory overclocking on Zen 3 then there’s no substitute for the Samsung B-Die RAM that makes up this kit, the G.Skill Ripjaws V 16GB DDR4-4000 CL16 – our recommended RAM kit for enthusiast Zen 3 builds. It’s very fast RAM with tight timings at the speed, and whilst it may not work optimally with the A-XMP profile applied there’s huge scope for manually tweaking timings and exploring optimizations. B-die kits can range from $100 to $500 or more depending on binning but it’s certainly not worth getting a top tier binned kit unless you’re intent on challenging world OC records. If you want to find out for yourself exactly what makes Zen 3 run sweetest, this is the kit for you.
Best RGB RAM for Ryzen Zen 3
We’ve got a soft spot for a set of four RAM sticks with synchronized RGB here at Premiumbuilds and the G.Skill Trident Z Neo DDR4-3600 CL18 kit certainly scratches that itch. The core specifications are solid with 3600MHz and CAS latency of 18 so your CPU will operate with a near optimum 1800MHz infinity Fabric Clock. G.Skill offer a very useful reverse QVL list so it’s easy to ensure compatibility with your chosen motherboard. The RGB can be controlled via any of Gigabytes RGB Fusion, Asus Aura Sync, MSi Mystic Light or Asrock Polychrome software so it integrates well with the rest of your RGB and doesn’t require stand alone software. The RGB elements are beautifully detailed and this kit will lend some real visual flair to your build.
Best 64 GB RAM Kit for Ryzen Zen 3
If your primary concern is the quantity of RAM – be it for a video edit workstation or scientific computation – then the Corsair Vengeance LPX 2x32GB DDR4-3200 CL16 kit is an excellent choice. Our benchmarks show minimal performance penalties at 3200MHz – RAM latency simply doesn’t impact tasks like rendering in the same way as it does gaming – but this is still 3200MHz RAM with CAS latency of 16 and performs well enough for AMD to showcase their new top tier GPU’s using RAM of this specification. Corsair are a long-standing brand and their LPX line is ubiquitous so obtaining matched RAM for future expansion won’t be a problem. Corsair also offer a 3600MHz LPX kit but supply is patchy and with a CAS latency of 18 the actual memory latency is nearly identical to this kit. If you need to pack as much RAM as possible then sacrificing a little speed for cost and capacity makes sense which is why this kit is a great buy.
Benchmark Notes
The tests were conducted using the Premiumbuilds test bench, which comprises a Ryzen 5800X, MSI B550 Mortar Motherboard using AGESA 1.1.0.0 Patch C BIOS. RAM used was the Patriot Viper PVS416G440C9K 4400Mhz Samsung B-die Kit. PBO was activated but no manual CPU overclocking was undertaken. Timings under test were as follows
| Speed | Timings CL-tRCD-tRP-tRAS | FClk | Voltage | CPU PBO |
| 4000MHz C16 | 16-16-16-34 | 2000 MHz 1:1 | Auto (1.4 Max) | ON |
| 4000MHz C18 | 18-18-18-34 | 2000 MHz 1:1 | Auto (1.4 Max) | ON |
| 3800MHz | 16-16-16-34 | 1900 Mhz 1:1 | Auto (1.4 Max) | ON |
| 3600MHz | 16-16-16-32 | 1800 MHz 1:1 | Auto (1.4 Max) | ON |
| 3000MHz | 16-16-17-34 | 1500 MHz 1:1 | Auto (1.4 Max) | ON |
| 2133MHz | 15-15-15-36 | Auto (default) | Auto (1.4 Max) | ON |