Testing 4000MHz RAM: content creation

Exploring video rendering and probing the theoretical limits.

In traditional fashion, let's take a look at some quick content creation benchmarks before we get into the gaming tests.

Cinebench R20 is an industry-standard test of CPU power, with both single-threaded and multi-threaded workloads, and mimics the rendering of a 3D scene in Cinema 4D. We also tested video transcoding, a common task for any video producer, using the excellent open source Handbrake tool. Our test involved transcoding one of our Patreon video files to x264 and x265 (HEVC) using the Production Standard preset and CRF 18 quality setting.

First, let's take a look at our results testing the 4000MHz kit at its standard CL19 timings - plus results from when we increase the voltage from 1.35V to 1.40V for a quick-and-dirty overclock to 4200MHz. You can see that the single-threaded results show some variance between runs, but no clear increase from the higher frequency, but the multi-threaded results do trend slowly upwards as frequency ramps up, with that increase more-or-less stopping after 3600MHz. Given that AMD previously identified 3600MHz as the point at which diminishing returns start to kick in, perhaps that's not too surprising.

The Handbrake tests show similar results, with very little variance each time we tick the frequency 200MHz higher, with 4200MHz providing just a two per cent uplift in the HEVC encode frame-rate compared to 3200MHz. The H.264 encode is similarly uneventful, with run-to-run variance basically drowning out any performance gains. I think it's safe to say that, at least on our 9900K-based test rig, content creators won't see any appreciable increases to performance in these sorts of tasks from the use of higher RAM speeds.

We also recorded power usage at the wall from these tests, which seemed to flip between ~195W and ~210W whenever we increased frequency by 200MHz - weird!

9900K Content Creation CB R20 1T CB R20 MT HB h.264 HB HEVC HEVC Power Use
4200MHz CL19 1.4V 491 3838 29.48fps 13.62fps 196W
4000MHz CL19 497 3825 29.54fps 13.52fps 216W
3800MHz CL19 484 3808 29.37fps 13.54fps 196W
3600MHz CL19 494 3820 29.08fps 13.40fps 210W
3400MHz CL19 497 3797 29.29fps 13.42fps 195W
3200MHz CL19 490 3776 29.07fps 13.36fps 209W

Now, let's see what happens when we throw tighter timings into the ring. The excellent DRAM Calculator for Ryzen can also be used to suggest timings on Intel-based systems, but sadly doesn't seem to support the 4000MHz speeds we're using. We selected the highest frequency it did support, 3600MHz, and provided the rest of the data it required. It suggested primary timings of 16-17-17-34, compared to our stock 19-23-23-45, and we dutifully entered that into the BIOS, leaving the secondary and tertiary timings at their ASUS-optimised defaults for now. We'll only be running these timings for a short period, so we pushed voltage up to 1.4V and recorded our results.

Tightening our timings pushed up our Cinebench results against the CL19 counterparts from 3200MHz to 3600MHz, but then didn't provide much of a boost beyond that. In Handbrake, we recorded a new high scores for both h.264 and h.265 tests at 4000MHz CL16, but the overall increases were only around one per cent.

9900K Content Creation CB R20 1T CB R20 MT HB h.264 HB HEVC HEVC Power Use
4000MHz CL16 1.4V 492 3833 29.77fps 13.66fps 212W
3800MHz CL16 1.4V 497 3827 28.94fps 13.36fps 205W
3600MHz CL16 1.4V 496 3831 29.55fps 13.62fps 214W
3400MHz CL16 1.4V 492 3839 29.60fps 13.61fps 196W
3200MHz CL16 1.4V 494 3826 29.48fps 13.54fps 196W

Given what we've seen so far, we don't expect to see massive changes from one RAM manufacturer to another, but let's look at the same tests performed on the same systems with slower XMP speeds, from 3200MHz to 3600MHz, all at CL16 with "XMP I" set in the BIOS.

The RAM sticks we used for this test are all 2x8GB kits:

Perhaps unsurprisingly, we see very little difference between our 4000MHz RAM at 3600MHz CL16 and different RAM with a 3600MHz CL16 XMP setting. That's good, as it suggests our results here from our Corsair 4000MHz kit will be more broadly applicable.

9900K Content Creation CB R20 1T CB R20 MT HB h.264 HB HEVC HEVC Power Use
3600MHz CL16 (XMP) 496 3838 29.75fps 13.61fps 214W
3400MHz CL16 (XMP) 492 3813 29.61fps 13.61fps 210W
3200MHz CL16 (XMP) 493 3823 29.35fps 13.43fps 195W

Before we get into our game testing, let's have a quick look at how all of these kits perform in their various configurations in a standard synthetic benchmark for RAM bandwidth testing: AIDA64's memory tests. These tests include four RAM-specific results we're interested in - read, write and copy times - plus a measure of latency. This should give us an idea of how the different configurations differ in raw performance, showing us how much of a performance difference we could expect in cases where RAM, not CPU or GPU, is the limiting factor.

The results here are pretty straightforward, with read, write and copy speeds increasing by around 2000MB/s to 3000MB/s for each additional 200MHz of frequency. Stepping from CL19 to CL16 seems to provide another 3000MB/s in read speeds, but has a smaller effect (~1000MB/s) on write speeds. Latency is unsurprisingly mostly affected by timings, with figures in the high forties or low fifties at CL19 and the lowest to mid forties at CL16. Note that there was more run-to-run variance here, which may explain the very low latency at 4200MHz CL19 compared to the other CL19 results.

9900K Aida64 Read Write Copy Latency
3600MHz CL16 (XMP) 51483MB/s 51256MB/s 46215MB/s 43.7ns
3400MHz CL16 (XMP) 51412MB/s 48444MB/s 44781MB/s 44.0ns
3200MHz CL16 (XMP) 45997MB/s 45125MB/s 40756MB/s 47.0ns
4000MHz CL16 1.4V 55398MB/s 56622MB/s 50872MB/s 41.2ns
3800MHz CL16 1.4V 53205MB/s 54115MB/s 48169MB/s 42.5ns
3600MHz CL16 1.4V 50709MB/s 50850MB/s 46434MB/s 44.5ns
3400MHz CL16 1.4V 48532MB/s 48178MB/s 43458MB/s 45.0ns
3200MHz CL16 1.4V 45870MB/s 45132MB/s 40552MB/s 46.6ns
4200MHz CL19 1.4V 54946MB/s 58425MB/s 49796MB/s 43.7ns
4000MHz CL19 51556MB/s 54901MB/s 47123MB/s 50.9ns
3800MHz CL19 50546MB/s 52929MB/s 45664MB/s 48.2ns
3600MHz CL19 48261MB/s 50123MB/s 43319MB/s 50.4ns
3400MHz CL19 46824MB/s 47483MB/s 41709MB/s 49.2ns
3200MHz CL19 44298MB/s 44607MB/s 39353MB/s 50.7ns

From 3200MHz CL19 to 4200MHz CL19, we see a 24 per cent increase in read speeds, a 31 per cent increase in write speeds and a 27 per cent increase in copy speeds. If we instead compare 3200MHz CL19 to 4000MHz C16, we get similar figures, between 25 and 30 per cent. These should be close to the theoretical maximum upticks we could expect in any workload from switching from 3200MHz to 4000MHz RAM, with actual performance improvements being dependent on a range of other factors and therefore likely to be much lower, as we already saw with the minute changes to our content creation results.

With that out of the way, let's move onto what we really care about - gaming - where we expect to see more noticeable performance improvements when swapping standard 3200MHz for higher-spec RAM.

Testing 4000MHz RAM: Are higher frequencies worth it?

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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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