A Lighter Touch: Exploring CPU Power Scaling On Core i9-13900K and Ryzen 9 7950Xby Gavin Bonshor on January 6, 2023 8:00 AM EST
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.