A Lighter Touch: Exploring CPU Power Scaling On Core i9-13900K and Ryzen 9 7950X
by Gavin Bonshor on January 6, 2023 8:00 AM EST- Posted in
- CPUs
- AMD
- Intel
- 65W
- TDP
- Ryzen 9 7950X
- Core i9-13900K
- Power Scaling
- Efficiency
- 105W
- 125W
- 253W
- 230W
- PPT
Core i9-13900K & Ryzen 9 7950X Scaling Performance: Peak Power/Temps & Gaming
In our gaming performance testing, we're using two very different titles to measure any gains (if any) when dropping the power on the Core i9-13900K and Ryzen 9 7950X. The first title is Total War: Warhammer 3, which is notoriously hungry in terms of processor performance. We felt this would be a good measuring stick to see how performance stands as we restrict power to the processor. The second title is Borderlands 3, which albeit more graphically intensive than TW: Warhammer 3, still benefits from processing power as many other titles do.
We'll first go over the peak package power and core temperatures.
Peak Power and Core Temperature: Feat yCruncher and AIDA64
One of the main benefits of reducing power consumption and electrical load on a component is temperature; less power means less heat. As we reduce the TDP and test with power restrictions, we should also see a noticeable reduction in heat and CPU core temperatures. To measure the peak package power load from the CPU and to determine the peak core temperatures, we are using AIDA64 to record both variables. Putting full load on the CPU is yCruncher, which we use to measure peak processor package power in our CPU reviews.
Starting with the peak power figures, it's worth noting that AMD's figures can be wide off the mark even when restricting the Package Power Tracking (PPT) in the firmware. For example, restricting the socket and 7950X to 125 W yielded a measured power consumption that was still a whopping 33% higher. By comparison, the 13900K exceeded its set limits by around 14% under full load. In all cases though, this is still a significant power reduction versus their stock settings, especially in the case of the power-hungry i9-13900K.
Following on from the temperatures, despite pulling a figure of 330.3 W under full load, the peak core temperature of the i9-1300K was 8°C lower than the Ryzen 9 7950X, which hit 94°C under full load. Given that the power figures given aligned more with the settings on the 13900K than they did on the 7950X, the drop in temperatures on the Intel processor was much better received, with 53°C at 125 W and just 39°C at 65 W.
There's certainly more performance at 65 W from our compute testing on the Ryzen 9 7950X, but it's drawing more power than it should be. It's also running hotter despite using a premium 360mm AIO CPU cooler, which is more than enough even at full load. As a reference, the room that all the testing was done at ranged between 22 and 24°C, so this shouldn't impact any of our thermal results too much.
Total War: Warhammer 3: 1080p Ultra and 4K Medium Settings
In Total War: Warhammer 3, we saw something very interesting. Dropping the power on the AMD Ryzen 9 7950X, even down to just 35 W, didn't seem to impact performance at either 1080p Ultra or 4K Medium settings. In both cases we're performance-bound by other factors, be it single-threaded performance or GPU performance. This is a good precedent being set here by AMD, as even at such a low power, it's not enough to warrant noticeable drops in framerates, which is partly down to utilization with our AMD Radeon RX 6960 XT graphics card.
Touching on the Intel Core i9-13900K, although average frame rates and 5% lows at 1080p remained stable and similar, the 5% lows were much less desirable when testing at 4K. Average frame rates seem stable, but having much lower 95th percentile frames could become troublesome depending on the title, visual settings, and utilization of both CPU and GPU at lower power. Though, like many benchmarks relating to games, this phenomena is going to vary on a game-by-game basis.
Borderlands 3: 1080p and 4K Ultra Settings
Looking at performance in Borderlands 3, we can see that both the Core i9-13900K and Ryzen 9 7950X perform well even at just 35 W. This shows how powerful both these chips are for gaming, with high core counts which, despite operating at much lower power than stock, that it doesn't affect performance too much.
The only real notable result in Borderlands 3 was the Intel Core i9-13900K at 1080p, with lower 5% low framerates than the Ryzen 9 7950X. Although this could be an anomaly, we tested this three times, and all the results were similar. Even so, at just 35 W, the performance in gaming was typically unaffected, which shows that the game is more often waiting on our Radeon RX 6950XT video card.
Of course, gaming performance isn't going to be too much of a war of attrition to seek benefits even at lower power envelopes on the processor at resolutions such as 1440p and 4K, where performance is primarily GPU-limited. Even at 1080p, where there's a cross-over between CPU and GPU utilization, performance is still good.
There will certainly be a big difference at lower resolutions, such as 720p and lower. Still, users looking at a $500-600 processor, a $300-500 motherboard, and $150+ for memory are highly unlikely to be gaming at these resolutions, so we focused more on the realistic scenarios in gaming as opposed to purely synthetic ones.
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cbutters - Friday, January 6, 2023 - link
Would be really cool to see this type of content for the GPU side of things... The 4090 seems to be VERY efficient and retains performance even when reducing the power drastically.icoreaudience - Friday, January 6, 2023 - link
These results should really be reported using an external power meter.The reports from internal probes can be incorrect, if not "doctored", and the "command" to enforce a given power limit can be widely interpreted, as evidenced by some of these tests.
On this last point, AMD is the worst cheater, with > 30% difference between the "claimed" power limit and the reported one. This has worked well for them, since they can score "great" performance results at low TDP ... just by not respecting the TDP.
This is an important point, because as long as news outlets continue to fall for this false reporting trick, there will be a direct incentive for chip manufacturers to cheat even more. Pretty soon, we'll have meaningless "TDP limit", and countless "tech expert" praising the efficiency of the one that cheats the most.
tygrus - Friday, January 6, 2023 - link
You could spend more time ensuring the power caps can be the same in practice (your caps were in theory but not followed by CPU on average).It does show that Intel performance/power curve is flatter & rewards greater power usage. AMD perf/pwr curve is flatter so it doesn't pay to overclock it but does reward underclocking. Just imagine if AMD could keep its low freq efficiency but get Intel scaling on top.
Cooe - Friday, January 6, 2023 - link
TL;DR = AMD's going to absolutely MURDER Intel in laptops this generation. Dragon Range-HX vs Raptor Lake-HX is going to be an absolute freaking bloodbath in AMD's favor...corinthos - Sunday, January 22, 2023 - link
why are the likes of ASUS dropping AMD and going Intel-only this next gen for their laptop lines then?trenzterra - Friday, January 6, 2023 - link
Is there a reason why Intel has such low temps compared to AMD at the same power usage? Seems like in a SFF PC or laptop using Intel would mean a cooler chassis despite drawing more power?cyrusfox - Friday, January 6, 2023 - link
Look at the actual power used, AMD seems to be sipping 30 watts more than advertised, that is likely one reason, the other has to be the IHS with the chiplets, probably not providing good equal contact as well as the IHS being much thicker, See derbauer's video on that from June 2022 "Very thick IHS and less Contact Area - some thoughts on Ryzen 7000"Harder to transfer that heat when the IHS is more insulating and slowing the transfer out of the chip into the heatsink. Intel will always win temp to temp comparison unless it is delidded.
HideOut - Friday, January 6, 2023 - link
Or you can buy one of those newly announced non X varients of the AMD chips. Lower costs and lower power out of the box.mirancar - Saturday, January 7, 2023 - link
gavin, can you please also measure actual power usage from wall socket. from other reviewers there was a big obvious difference between amd’s tdp and intel’s tdp. then you should try to match the tdps to actual power. also would be nice to try and recomend best settings for both processors. i ordered a 13900k and i plan to run it on around 180-200w tdp, where i am hoping for max 75c on full load with a nh-d15Hresna - Tuesday, January 17, 2023 - link
I measured wall power for my 13900k using a self-reporting corsair PSU and hwinfo logging. My system has high idle power because of some power hungry components but it gives a more detailed view of how the power scaling metrics pan out. My results available here:https://www.reddit.com/r/hardware/comments/10bna5r...