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Core i9 9900KS: does faster RAM improve gaming performance?

Intel and AMD tested.

We continue our investigations into RAM speeds with a brief analysis of the RAM situation with the 9900KS. In theory, we should see similar margins here with the 9900K and 9900KS, but it's also important to see how these Intel processors compared against those from AMD. Historically, AMD is known as being more sensitive to memory speeds, with third-gen Ryzen seems better equipped with work with slower RAM than its predecessors.

We're using the same dual-channel 16GB G.Skill kit here as in our recent Ryzen reviews, the totally over-the-top Trident Z Royal. The idea is to run our benchmarks at 3600MHz, the rated speed of this RAM, then step back down to 3000MHz to see how much of a performance penalty the lower frequency introduces. We looked at three games from our test suite here - Far Cry 5 and Crysis 3, which we've seen in earlier pages, as well as Ashes of the Singularity. In all cases, we're testing at ultra settings at 1080p resolution.

Interestingly, the 9900KS seems more dependent on memory speed at 5GHz than the 9900K at 4.7GHz, losing a greater percentage of performance in Ashes of the Singularity Escalation and Far Cry 5. This result is a little odd, but persisted through repeated testing. Ashes is probably the most RAM-sensitive benchmark we have, so the 10 per cent performance loss here is probably a worst-case scenario. Crysis 3 also shows performance degradation moving from 3600MHz to 3000MHz, but the difference here is still quite minimal at around two per cent.

Apart from the 9900KS performance, the broad strokes are that AMD's third-generation Ryzen processors are less sensitive to RAM speeds than their predecessors, but opting for fast kits around the 3600MHz mark does result in a noticeable uptick in performance at 1080p. High-speed RAM is becoming gradually more affordable, so it's well worth considering if you can find a dual-channel kit within your budget. If you can't, then you may be able to make up some of the gains by overclocking the Infinity Fabric that links different components on the chip beyond RAM speed. Either way, it's well worth experimenting if you're using AMD hardware.

Meanwhile, Intel seems to better make do with slower RAM, but there's still a measurable advantage to be had by opting for a faster kit. We'll conclude this section by mentioning that Intel restricts memory overclocking quite severely unless you're running a high-end 'Z' board, while AMD allows memory overclocking on much more affordable motherboards. We recommend comparing full system prices to get a better understanding of value, rather than looking at processor versus processor in isolation.

Ashes of the Singularity: CPU Test

Far Cry 5: Ultra, TAA

Crysis 3: Very High, SMAA T2X

Intel Core i9 9900KS analysis

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Will Judd avatar

Will Judd

Deputy Editor, Digital Foundry

A bizarre British-American hybrid, Will turns caffeine into technology articles through a little-known process called 'writing'. His favourite games are Counter-Strike, StarCraft and Fallout 2. Will also tweets the latest tech deals at @DealsFoundry.


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