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Core i5 10600K and i9 10900K: Memory bandwidth analysis

AMD and Intel tested.

Our final testing area is all about RAM. Love it or hate it, you can't game without it - and faster memory frequencies can boost performance in CPU-bound scenarios, depending on the game and the processor in question. We've opted to test at two memory frequencies: the 3000MHz that now serves as the baseline for new RAM purchases and the more enthusiast-grade 3600MHz that's a sensible upgrade choice for high-end systems.

To test the effects of memory speed, Crysis 3 and Far Cry 5 are joined by real-time strategy title Ashes of the Singularity Escalation. This latter test uses the game's brilliant built-in benchmark, which helpfully includes all of the processing performed in real gameplay, with the twist that units can't take damage so the number of aircraft and hovertanks on-screen remains ludicrously high throughout.

You can immediately see the effect that RAM speed has in the Ashes test. The 10th-gen Core i9 model loses around eight per cent of its performance, dropping to around the same level as its Core i5 counterpart at 3600MHz, while the Core i5 sees a nine per cent drop in performance when running with slower memory. If Ashes is representative of all games then we'd recommend going for a mid-range review and fast RAM... but as we'll see later, not all games scale so drastically.

Ashes of the Singularity: CPU Test

  • i9 10900K
  • i9 10900K
  • i5 10600K
  • i5 10600K
  • i9 9900K
  • i9 9900K
  • i7 9700K
  • i7 9700K
  • i5 9600K
  • i5 9600K
  • R9 3900X
  • R9 3900X
  • R7 3700X
  • R7 3700X
  • R5 3600X
  • R5 3600X
  • R3 3300X
  • R3 3300X
  • R3 3100
  • R3 3100
  • R7 2700X
  • R7 2700X

Far Cry 5 is something of a return to normalcy then, with the high dependence on single-core speed allowing the Core i9 10900K to reclaim its position at the top of the stack with an average of 170fps, which drops just five per cent when the flagship processor is paired with more pedestrian 3000MHz RAM. The Core i5 model again exhibits a smaller loss in performance, around 2.5 per cent, which more closely resembles our results from the 9900K and 9700K. If we take a look in Ryzen land, the 3900X and 3600X lose just a single percentage point, but something like a six per cent drop is typical for other Zen 2 CPUs we've tested.

Far Cry 5: Ultra, TAA

  • i9 10900K
  • i9 10900K
  • i5 10600K
  • i5 10600K
  • i9 9900K
  • i9 9900K
  • i7 9700K
  • i7 9700K
  • i5 9600K
  • i5 9600K
  • R9 3900X
  • R9 3900X
  • R7 3700X
  • R7 3700X
  • R5 3600X
  • R5 3600X
  • R3 3300X
  • R3 3300X
  • R3 3100
  • R3 3100
  • R7 2700X
  • R7 2700X

The final game we tested at multiple frequencies is the Crysis 3. This test shows that some games don't care too much about memory bandwidth when run on a modern CPU, with almost all results showing differences within the margin of error - just one or two percent, effectively meaningless when you're hitting 140 to 200fps! However, do note that earlier Zen and Zen+ AMD CPUs we tested did show a heavier reliance on memory speed that was evident in this test, with the likes of the 2700X losing almost ten per cent of their performance when dropping from 3600MHz to 3000MHz!

Crysis 3: Very High, SMAA T2X

  • i9 10900K
  • i9 10900K
  • i5 10600K
  • i5 10600K
  • i9 9900K
  • i9 9900K
  • i7 9700K
  • i7 9700K
  • i5 9600K
  • i5 9600K
  • R9 3900X
  • R9 3900X
  • R7 3700X
  • R7 3700X
  • R5 3600X
  • R5 3600X
  • R3 3300X
  • R3 3300X
  • R3 3100
  • R3 3100
  • R7 2700X
  • R7 2700X

From these results, we can see that RAM speed has a measurable performance impact on frame-rates for the Intel 10th-gen processors, ranging from relatively insignificant one or two percentage point differences in Crysis to bigger five, ten or even fifteen per cent differences in games like Far Cry 5 and Ashes of the Singularity. 3000MHz RAM remains our baseline recommendation, and opting for faster kits can be worthwhile too - especially for high-end builds using the Core i9 10900K, which seems more dependent on fast RAM than its Core i5 counterpart.

On an AMD processor review we'd conclude with that recommendation, but as these are Intel chips the RAM situation requires a little more explanation. Specifically, all 400-series chipsets apart from the premium Z490 platform - H470, B460 and H410 - suffer from memory speed restrictions. It's complicated too: 10th-generation Core i7 and i9 models support RAM speeds up to 2933MHz, while with a Core i5 or lower, the limit is 2666MHz. Anything beyond these frequencies is considered overclocking, which requires a £135+/$150+ Z-series motherboard, even if the RAM is rated for higher speeds.

In contrast, AMD doesn't restrict memory overclocking on a per-chipset basis, although higher-end motherboards are still more likely to support higher RAM speeds than their budget counterparts. Even the cheapest AMD B450 boards tend to support 3200MHz RAM though, with many offering 3600MHz or even 4000MHz support on motherboards that cost $120 or less.

Ultimately, these memory restrictions are confusing for consumers and damaging for Intel, especially the 2666MHz limit on Core i3 and Core i5 models. If you're considering the Core i5 10600, for instance, you're either railroaded into selecting an expensive Z490 motherboard you don't otherwise need, in order to get the benefit of 3000MHz memory, or you accept a non-Z motherboard and leave a significant amount of performance on the table by running your RAM at 2666MHz. Neither is a great option, and that could lead consumers to consider an AMD alternative to avoid these restrictions - especially when AMD chips also come with a great bundled CPU cooler, something that isn't true of Intel processors. Given the reality of the market in 2020, where 3000MHz is now the baseline frequency you'd expect rather than a lofty overclocking target requiring specialist equipment, Intel could and should do better.

Intel Core i9 10900K and Core i5 10600K analysis

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About the author

Will Judd

Will Judd

Senior Staff Writer, Digital Foundry  |  wsjudd

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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