AMD Ryzen 9 3900XT and Ryzen 7 3800XT: Memory bandwidth analysis

One of the most fascinating characteristics of the AMD Ryzen platform from the beginning has been its reliance on high-speed RAM in order to make up for the inherent latency disadvantage the platform faces due to its chiplet architecture. Third-gen Ryzen processors use much larger L3 caches, helping to ameliorate the problem, but high-speed RAM remains a key component of any AMD-based system. That's why we test with high-spec 3600MHz C16 DDR4 for all of our processor tests.

Thankfully, AMD allows for RAM overclocking even on its inexpensive motherboards - something not permitted on Intel's non-Z platforms - and RAM kit costs continue to fall, so outfitting your own system with fast memory is relatively affordable. In these tests, we'll look at two games we tested earlier, Crysis 3 and Far Cry 5, plus RTS title Ashes of the Singularity, to see how much performance you gain from switching from commonly available 3000MHz RAM to higher-grade 3600MHz RAM with the same timings.

In Ashes, the new XT models perform quite similarly to their predecessors, even dropping behind in some instances, with the faster RAM permitting an average frame-rate of between five and nine per cent. It's a similar story in Far Cry 5, where the difference is normally around six per cent. Crysis 3 is the least reliant on RAM for high-speed gameplay, with only a two or three per cent advantage for the new models when equipped with faster RAM.

Looking at Intel instead, the differences are normally more minor. Ashes is as bad as it gets for Intel, with differences of around eight per cent - a big enough drop that the Core i9 10900K at 3000MHz only manages the performance of a Core i5 10600K at 3600MHz! The differences are normally between three and five per cent in the Far Cry 5 test, closing to one per cent or less in Crysis 3.

So high-speed RAM remains more critical for AMD than for Intel, but this does change based on which game you're playing with some showing almost no difference in performance and some varying by up to 10 per cent. We look forward to investigating the effects of RAM frequency (and timings) on gameplay in future content, but let's leave it there for now.

AMD Ryzen 9 3900XT and Ryzen 7 3800XT analysis

• Introduction, hardware breakdown, test system
• Gaming benchmarks: Assassin's Creed Odyssey, Battlefield 5, Far Cry 5
• Gaming benchmarks: Crysis 3, Metro Exodus, Kingdom Come Deliverance, The Witcher 3
• Gaming benchmarks: Memory bandwidth analysis [This Page]
• AMD Ryzen 9 3900XT: the Digital Foundry verdict