Core i9-13900K & Ryzen 9 7950X Scaling Performance: CPU Short Form

For the compute side of our testing to determine how well the Core i9-13900K and Ryzen 9 7950X scale at different power levels, we've opted for a range of CPU-intensive benchmarks, particularly from the rendering and encoding section of our test suite.

To keep the playing field even, we are using the same SK Hynix DDR5-5600B 2 x 16 GB memory kit throughout all of our testing. We've separated the results within the same graph to outlay performance differences at different power levels so that users can see the differences and comparison in performance on offer from both the Core i9-13900K and Ryzen 9 7950X processors.

CineBench R23: Single and Multi-Threaded Performance

CineBench R23 Single Thread

CineBench R23 Multi-Thread

Focusing on performance in CineBench, it is worth highlighting that in the single-threaded test, Intel's Core i9-13900K displayed better single-core performance throughout. It didn't impact single-threaded performance on either processor despite restricting the power levels, which is exactly what we'd expect to find. While highly clocked CPU cores are very expensive from a power perspective, they are not so expensive as to consume the complete power budget of chips such as these.

Looking at multi-threaded performance in CineBench R23, this is where restricting the power levels makes the difference. Although Intel has the best performance in CineBench R23 MT at stock settings, it's AMD that scales better (i.e. loses less performance) as the power is restricted. Even at 65 W, the Ryzen 9 7950X is faster than the Core i9-13900 at 125 W, which is very impressive. Both processors take a massive hit in performance at 35 W, which is to be expected as we're now some 200 Watts below their stock power limits.

C-Ray 1.2: 4K, 16 Rays Per Pixel

C-Ray 1.2: 4K, 16 Rays Per Pixel

Looking at the results in our C-Ray benchmark, the results between stock settings to 65 W impacted our figures. Starting with the Ryzen 9 7950X, there was a marginal performance loss between stock settings at 125 W and 105 W. Going from stock settings to 65 W (2.5X power), there was a drop in C-Ray performance of around 16%.

Focusing on the Core i9-13900K, its performance was heavily power reliant when comparing stock settings to 125 W, 105 W, and 65 W. Even from stock settings to 125 W, there's a performance loss of around 21%, and even more so comparing stock settings to 65 W, which equates to around 38%.

Things tailed off massively when both set to 35 W, with the AMD Ryzen 9 7950X beating the Intel Core i9-13900K convincingly here.

POV-Ray 3.7.1: 

POV-Ray 3.7.1

In our POV-Ray benchmark, we saw some interesting behavior. Although the Core i9-13900K at default settings comfortably beat the Ryzen 9 7950X, the 7950X held its performance well when dropping down the power, with the 7950X's result at 65 W being similar to the 13900K at 105 W. This shows that the Ryzen 9 7950X and its 5 nm die is more scalable at lower power.

Blender 3.4: CPU Only Compute

Blender 3.4 BMW27: ComputeBlender 3.4 Classroom: ComputeBlender 3.4 Fishy Cat: Compute

At default settings, the Core i9-13900K and Ryzen 9 7950X was competitive in all of the Blender sub-tests, even when restricting the power. Once power was restricted, we saw that the 7950X held onto much of its performance, while the 13900K didn't fare so well. In the Fishy Cat subtest at 65 W, the 7950X was 62% faster than the 13900K, which is impressive scaling here by AMD.

x264 Encoding: 1080p and 4K Bosphorus

x264, Bosphorus 1080px264, Bosphorus 4K

The x264 benchmark focuses on encoding performance, and at default settings, AMD's Ryzen 9 7950X wins out. Even dropping down to 125 W, the 7950X only loses around 2% at 1080p and around 4% at 105 W. At 65 W, the 7950X is around 16% slower than at default settings.

Looking at Intel's Core i9-13900K, the 13900K loses around 15% performance by restricting power to 125 W compared to default settings. This is another example that the 5 nm Zen 4 architecture scales much better at lower power envelopes than Intel's 10 nm refresh; this isn't unexpected, however.

Exploring CPU Power Scaling On Core i9-13900K and Ryzen 9 7950X Core i9-13900K & Ryzen 9 7950X Scaling Performance: Peak Power/Temps & Gaming
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  • allenb - Sunday, January 8, 2023 - link

    Just adding to what others have said, but this is great data. One of the more interesting articles I've seen here in some time. Keep it up!
  • alanritchie - Sunday, January 8, 2023 - link

    Would be really useful to see a total joules reading from a power meter for a selection of the gaming results that show no performance gains (so the GPU isn't doing any more work). Does the CPU use 200W and but not achieve any more than the 65W, or does it use less than 65W to reach peak performance (35W in Borderlands) on whichever thread is limiting the FPS?

    The weird one is the TW 4k 95th percentile test, 35W and 125W are within touching distance of each other, but full power suddenly unlocks another 20FPS.

    Essentially, if I power limit the CPU and only play games, am I actually saving any power in most games, or does the CPU just not use the available power because it is GPU limited, so both the performance and the electricity bill are the same with a 65W limit, 125W limit or no limit?

    Also would be nice to see total J for the other benchmarks, but I think its a lot more obvious that the extra power is going into extra performance in most of them, even if they get less efficient
  • Jase76 - Sunday, January 8, 2023 - link

    Great work Anand, Love this article!

    As a SFF PC owner, it's a struggle to balance performance and power budgets so this sort of analysis is a godsend.
    Power usage is not just about power bills for me, default CPU settings will max out the cooling solutions turning the PC into a very noisy hair dryer! It's not desirable to say the least.
    I'll second other's suggestions about measuring actual power usage for Performance per watt metrics. The AMD CPU is still very hot at 105W which seems suspect.
  • ricebunny - Monday, January 9, 2023 - link

    I found it confusing how the term “scaling” was used in the article. Clearly, the Intel CPU was more responsive to power while the AMD CPU had near saturated performance from 105W upwards. If I had to write the report myself, I would’ve said that the Intel CPU scaled better with power based on the data points.
  • leavenfish - Wednesday, January 11, 2023 - link

    I actually think the most useful thing for the average person would be - what is the 'W' at which each processor can run WITHOUT a watercooler - 65W? 105W? Just with a good case and fans. These people are not interested in the upkeep and fear associated with water-cooling so it would be very useful information.
  • ABR - Thursday, January 12, 2023 - link

    Wow. I know server chips are tuned further down the curve, but I don't think as far down as that 65W, relatively speaking. This could have massive implications at the data center level.
  • Jp7188 - Monday, January 16, 2023 - link

    @Gavin great investigation. I love stuff like this.

    It would be nice to include actual power usage of the cinebench runs instead of assuming they used the same as the ycruncher runs in your calculations. I think that's a pretty big assumption. Could you perhaps do a couple of quick sanity checks of that assumption?
  • Jp7188 - Monday, January 16, 2023 - link

    I'd be interested to hear how each CPU reacts to different coolers. I can see someone using these in a HTPC config with a low profile cooler and limited fan speeds.
  • sorintt - Wednesday, January 18, 2023 - link

    You do not need power consumption measurement to see that AMD does not lower the consumption according to the setting. Just look at temperature.
  • Gastec - Friday, January 20, 2023 - link

    Oh, and you know that 100 W CPU that you've bought from us? That "W" actually doesn't stand for Watts anymore and it consumes 500 W-h when you fire up your favourite, exciting P2W video game.

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