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If you're thinking of upgrading to AMD's current AM5 platform, you're probably researching not just which CPU to buy, along with the supporting motherboard, but also which DDR5 memory kit you'll need.

To date, we've reviewed and tested almost all AM5 processors, along with countless 600 and 800-series motherboards. However, it's been some time since we looked at memory performance, so today we've got a quick update for you, focusing on G.Skill's new CL26 memory and DDR5-8000 performance.

Why we use DDR5-6000 CL30 Memory for Testing

Since the introduction of AM5, we've been testing with G.Skill's Trident Z5 Neo RGB DDR5-6000 CL30 memory, using a 32GB kit that currently costs $110 – a very reasonable price. AMD initially provided this memory to reviewers for evaluating Zen 4's performance, claiming it enabled optimal results while also stating that DDR5-6000 was the platform's sweet spot, which certainly held true for Zen 4.

With the release of Zen 5, AMD's messaging became a bit unclear. They continued to claim that DDR5-6000 was the sweet spot and recommended that reviewers use the same DDR5-6000 CL30 memory. At the same time, they promoted the new 800-series motherboards by claiming that X870 boards would provide the best performance thanks to support for DDR5-8000.

This was confusing for a few reasons, most notably because the 800 chipsets were essentially rebranded 600-series chipsets, refreshed for Zen 5. So, if an X870 motherboard supports DDR5-8000 memory, then the same should be possible on an X670 board – and this has since turned out to be the case.

However, it gets a bit more complicated because DDR5-8000 support is limited by the motherboard, not the Zen 5 memory controller or chipset. For example, when testing every single X870/X870E motherboard, we found that about half of the 21 boards tested worked with DDR5-8000, while the rest were unstable or simply failed to boot.

This testing was conducted using the same Ryzen 9 9950X CPU and DDR5-8000 memory, so the limiting factor was clearly the motherboard. It's possible that some of these boards could support DDR5-8000 with a BIOS update, but we haven't been able to confirm this yet.

As it stands, DDR5-8000 isn't ideal for all X870E motherboards, despite AMD's claims. Based on our past testing, it's also not necessarily an optimal configuration for performance – but we'll revisit that today.

The reason DDR5-8000 isn't always faster – or significantly faster – than DDR5-6000, despite a 33% increase in theoretical bandwidth, comes down to the frequency at which the integrated memory controller in the I/O die can operate. When running DDR5-6000, the memory clock is 3,000 MHz, and this can be matched by the UCLK (Unified Memory Controller Clock Frequency), which sets the speed for the memory controller. This allows the memory and controller to run in a 1:1 ratio at 3,000 MHz.

However, going beyond a DDR5 memory clock of 3,000 MHz forces the integrated memory controller to run at a 2:1 ratio, as it can't exceed 3,000 MHz while maintaining stability – at least for the majority of silicon. So, when using DDR5-8000, which runs at 4,000 MHz, the memory controller defaults to a 2:1 ratio and operates at just 2,000 MHz – 33% lower than with DDR5-6000.

That said, the additional bandwidth offered by DDR5-8000 can sometimes overcome the penalty of the 2:1 ratio, resulting in better performance – assuming your AM5 motherboard is stable at that frequency.

To find out how this plays out, we're comparing the Ryzen 7 9700X using DDR5-8000 with several DDR5-6000 configurations, including G.Skill's new CL26 memory, and we'll also include a baseline DDR5-5600 configuration. Many of you are probably curious about the 9800X3D, but we didn't include that CPU in this testing – it would have added a lot more work, and we already know it's not particularly sensitive to memory performance. This was most recently demonstrated with the 9950X3D, so DDR5 performance is more relevant to the non-3D chips.

Alright, let's get into the data…

Benchmarks

Cyberpunk 2077: Phantom Liberty

Starting with Cyberpunk 2077 at 1080p, we're seeing up to a 12% performance improvement when moving from the DDR5-6000 CL30 memory used in our reviews to the DDR5-8000 configuration, which delivered the best results. However, it was only 2% faster than the new DDR5-6000 CL26 memory. Unexpectedly, there was very little difference between the DDR5-6000 CL40 and CL30 configurations, and even the DDR5-5600 memory kept up closely.

Is DDR5-8000 Worth It? The Ryzen AM5 Test