Intel announced the Core i9-13900KS quietly at CES this year—no showing the CPU on-stage, or anything similar. Rather the company opted for a low-key release that was basically just a press release, with no launch-day reviews. In the meantime, AMD has unveiled their Ryzen 7000 X3D lineup, with the 7800X3D achieving impressive gaming performance that manages to beat the Core i9-13900KS. No doubt, Intel hoped for AMD's X3D plans to fizzle out, or materialize much later (as with Zen 3 X3D), but that didn't happen.

With the Core i9-13900KS, Intel is offering the world's first 6 GHz CPU—an impressive feat of technology, but it comes with an asterisk. Only two of the eight P-Cores are able to run at 6.0 GHz, and only if just one or two cores are active. The other cores will run at 5.6 GHz, this is also the case when multiple cores are loaded. The 13900KS includes the E-Cores that so much has been talked about in recent years. These "Efficient" cores are designed to handle light tasks like OS background activity with minimal energy usage, which frees up the P-Cores for more demanding tasks. The scheduling works very well these days, and there's no software to install, unlike AMD's Zen 4 X3D processors, which need properly working software drivers and game mode detection that relies on Microsoft's Game Bar app. Intel's Hybrid architecture, or the P-core and E- core approach isn't flawless though, there's still scenarios where Intel's Thread Director isn't working perfectly.

Under the hood, nothing has changed compared to the other high-end Raptor Lake processors. Actually, the 13900KS is the same piece of silicon as the 13900K, just with better binning, to achieve the higher clock speeds. The increased L2 caches of Raptor Lake are available, and the integrated graphics are UHD 770, too. What's changed is the default power limit, which has been bumped to 320 W (PL1=PL2) on high-end motherboards. While there's no official confirmation, it seems the differentiating factor is having two 8-pin EPS power connectors on the board. On lower-end boards, the power limit defaults to the same PL1=PL2=253 W as on the 13900K. Of course you're free to manually adjust the power limits to any setting you like, or disable them altogether.

Averaged over the 45 tests in our application test suite, the Core i9-13900KS can impress. It's clearly the fastest CPU in the test group, but the differences are small. Compared to the 13900K, the performance uplift is 3.5%, same as to the Ryzen 9 7950X. The 7950X3D is close behind, with a 6% gap. The gaming-focused AMD Ryzen 7 7800X3D is over 40% slower in applications—but much more affordable at the same time. Last generation's Core i9-12900K is 27% behind, not a bad gen-over-gen improvement. If your main focus is applications then the 13900KS is the fastest CPU you can buy today, but the alternatives are "close enough," especially once you factor in pricing. It is still impressive how Intel's 8 P-Cores, paired with 16 E-Cores are able to match or beat AMD's 16 "pure" Zen 4 cores.

The 13900KS is a mean gaming machine, too. Throughout our tests it delivers impressive framerates that are among the highest we've ever seen. However, the performance uplift to 13900K is minimal—less than 1% on average, especially at higher resolutions. Compared to AMD's Zen 4 processors without 3DV Cache, the deltas are around 10%; 5% at 4K. AMD's new Zen X3D processors come with improved gaming performance though. The Ryzen 9 7950X3D runs at virtually the same speed as the 13900KS, and the 7800X3D is even a little bit faster. These are tiny differences though—all of these processors will give you fantastic gaming performance. This also applies to "slower" CPUs like the 13700K, 13600K, 12900K, 12700K, other Zen 4 CPUs and more—the FPS differences are so small there really is no meaningful difference, especially at higher resolutions like 4K. There is some noteworthy differences in minimum FPS, but I'm not convinced that these are big enough to really change the experience during actual gameplay.

With performance so close, other qualities of the various processors become much more important, like power consumption and energy efficiency. Here the 13900KS is a winner, too, if the competition was "draw as much power as possible." In its default configuration, which sets "PL1=PL2=320 W," the processor consumed 350 W in demanding multi-threaded applications, setting a new record in power usage. In our 13900K review we were shocked by the 275 W power numbers of the 13900K, the 13900KS 1-up's this with ease. As mentioned before, Intel bumped the peak clock speeds on the KS, from 5.8 GHz to 6.0 GHz, which is a 3.5% increase, so not that much, and only for low-threaded scenarios. Not satisfied with that, I suspect they looked into other options to unlock more performance, and came to the conclusion that the power limit should be raised, once more. The problem is that not all motherboards have the current delivery capability required, so the 350 W increase was gated behind "automatically enabled on high-end motherboards." I tested this with an older BIOS from Dec 2022, which ran the 13900KS just fine, 6 GHz and everything, but 253 W PL1=PL2, just like the 13900K. With the newest BIOS, and everything set to "default," the power limit is changed to 320 W.

While few of our benchmarks show do some small performance gains that can be attributed to the higher power limit, I'm not convinced if this is the right direction. The power usage is so massive that I feel it will affect the value-proposition of Intel's new flagship. Especially when compared to AMD's Zen 4 offerings, the differences are staggering. During rendering, the 13900KS consumes 355 W, the 7950X needs 100 W less, while offering virtually the same performance. The 7950X3D even uses only 140 W, which is less than half of the KS, and it's only marginally slower. Similar situation in gaming: 13900KS average gaming power of 123 W, 7950X: 89 W, 7950X3D: 56 W, 7800X3D: 49 W (!)—all while offering virtually the same FPS. While I don't think the power cost difference will be a dealbreaker (75 W @ 4 hours per day @ 30 cents/kWh = $33 per year), the added heat dumped into the case and eventually into your gaming cave might make you reconsider.

Cooling such high heat output isn't easy on the CPU cooler either. Moving 350 W from a tiny silicon die, through a thick heatspreader is no easy task. Even with a large AIO sitting on top of the IHS you'll be close to 100°C when heavily loaded. With an air cooler you'll regularly thermal throttle. This is not a huge deal, as modern processors are very good at keeping a certain target temperature by slightly reducing clocks, without performance falling off a cliff—it's still not what you've spent all that money for. No doubt, you can undervolt the 13900KS, and dial the power limits back, but then why buy a KS in the first place? Things aren't much better on the Zen 4 side, because AMD wanted to keep cooler compatibility with Socket AM4, so they had to install an extra thick heatspreader on the AM5 CPUs, which make them difficult to cool, too, but it's easier due to the lower overall heat output.

Although the unlocked multiplier makes overclocking technically easy, it is limited by the cooling system. Even when the thermal limit is raised from 100°C to the maximum of 115°C, it is difficult to push voltage much further, even with an AIO. At least Intel is giving us the option to adjust the temperature limit, AMD has no such feature. Manual overclocking is also complicated by the fact that the low-thread count clocks on two cores are so high (6.0 GHz), while the other cores run at lower speeds. My highest all-core OC was 5.6 GHz, which results in minimal performance gains, because the CPU runs at 5.6 almost all the time anyway at stock. I think it's about time that Intel provided us with better overclocking controls for precision adjustments. Additionally, there is need for an overhaul of Intel XTU, as AMD's Ryzen Master provides a superior user experience. It's high time for Intel to update their boosting technologies as they are still relying on almost decade-old algorithms. In contrast, AMD has been consistently refining their methods every few years and is achieving significant improvements by incorporating more fine-grained mechanisms that consider many more variables on the running system.

Intel has announced an MSRP of $700 for the 13900KS, which matches the AMD Ryzen 9 7950X3D. Compared to the 13900K, the price increase is $130—for a few percent in performance and some extra power consumption—very hard to justify. On the other hand you're getting a processor that impresses with fantastic performance in all areas—applications and gaming. With the Ryzen offerings you'll have to make more compromises: the 7800X3D is the best processor for gaming, and only $450, but it's a bit slower in applications. The 7950X3D is among the fastest in gaming and applications, but requires custom AMD software for game detection and processor thread management that doesn't always do the right thing. For a more application-focused experience you could opt for the 7950X, but you'll be losing out on a bit of gaming performance due to lack of 3DV cache and the dual CCD design. At the end of the day all these processors are really really good at everything and you'll have a hard time noticing much of a subjective difference. On the other hand, I can imagine a lot of people out there with deep pockets that want "the fastest," especially for content creation, who don't care much about power and also like the bragging rights for having the Limited Edition KS. For the vast majority of gamers and users out there, a 13700K or 7700X would be the much better choice—not much slower, but the motherboard and memory can be bought for the price difference to the 13900KS. Last but not least, 5800X3D is a great gaming option, too. Let's hope that Intel's Meteor Lake can make progress with power efficiency, and then everything else will come together, too—they have the IPC and performance.