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Intel Core i9-12900K review: Alder Lake at its most extreme

Intel’s top chip is literally a hot prospect

By now you’ve probably heard about how Intel’s 12th Gen Alder Lake CPUs shake up the previously stagnant Core line. Led by this, the Intel Core i9-12900K, Alder Lake sees the adoption of a hybrid architecture that combines high-power Performance cores (P-cores) with Efficiency cores (E-cores) that can free up headroom by taking on background tasks. The Core i9-12900K takes this opportunity to bulk up, combining eight P-cores and E-cores apiece for a total of 16 cores and 24 threads.

For a gaming PC, this looks like lunacy – the endearingly ambitious kind, but lunacy nonetheless. And yet Intel’s i9 parts have always delivered the goods when it comes to at-all-costs gaming performance, with not even the mighty AMD Ryzen 9 5950X quite matching up in games even as it spanks Intel in multitasking. As expensive as the Core i9-12900K is, it’s still cheaper than the 5950X, so could it be the new aspirational CPU to beat?

To find out, I set it up in the same test bench that I used for our Intel Core i5-12600K review, including the Asus ROG Maximus Z690 Hero (£520 / $600) motherboard and 16GB of Geil Polaris RGB DDR5 memory. Again that means dealing with the RAM’s deeply unimpressive 40-40-40-77 timings, though its 4800MHz frequency helps counterbalance such high latency to the point of broad comparison with our usual DDR4 RAM. If you’re thinking of upgrading to an Alder Lake chip, rest assured you’ll have a choice of DDR5- or DDR4-compatible mobos.

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Even with Turbo Boost Max, the Core i9-12900K’s P-core frequencies don’t reach quite as high as those of its predecessor, the Core i9-11900K; these new cores have a base clock of 3.2GHz and a peak boost speed of 5.2GHz. The E-cores, to which previous-gen chips don’t have an equivalent, come in at 2.4GHz base and 3.9GHz boost.

Two sticks of Geil RGB DDR5 RAM installed in a motherboard.

These specs might give the impression that the Core i9-12900K is trading single core heft for a more Ryzen-eque multitasking affinity, but that’s only half true. As it happens, this is the highest-scoring chip we’ve ever tested in the Cinebench R20 single core test, with fellow Alder Laker the Core i5-12600K in second place:

A bar chart showing how the Intel Core i9-12900K performs against other CPUs in the Cinebench R20 single core test.

As for the multicore test, the 32-thread Ryzen 9 5650X comes close, but Intel can finally claim to have beaten AMD on multitasking as well as gaming. As with the Core i9-12900K, this result is a major win for the hybrid architecture, showing that the ability to offload tasks to E-cores (while keeping the more powerful P-cores free for heavier lifting) is no mere party trick. Intel’s Thread Director tech deserves a mention here are well: this feeds extra information on loads and temperatures to Windows’ own task scheduler, which makes the latter more effective at assigning processes to the most appropriate cores.

A bar chart showing how the Intel Core i9-12900K performs against other CPUs in the Cinebench R20 multicore test.

The closest thing to a downside with this system is that although it’s perfect for workstations, or just heavy desktop multitasking, the gaming applications are relatively limited. As such, the Core i9-12900K does generally perform better than the Ryzen 9 5950K and/or Core i9-11900K, just not by such sprawling margins.

A bar chart showing how the Intel Core i9-12900K performs against other CPUs in various games.
A bar chart showing how the Intel Core i9-12900K performs against other CPUs in various games.

This was the case with the Core i5-12600K as well, though it’s hard to be as understanding when the i9 costs the best part of £600 – I think for that kind of cash it’s fair to expect bigger jumps from the previous generation. Still, the new model can produce better results in games that are built to take advantage of multiple threads; Assassin’s Creed Valhalla shows an especially wide lead on the Ryzen 9 5950X. Forza Horizon 4 gets a double-digit frame rate advantage too, albeit at a level where you’d need one of the best gaming monitors and some eagle eyes to tell the difference.

An Asus ROG Maximus Z3690 motherboard with RAM, CPU and cooler installed.

Alongside the feature set common to all Alder Lake chips – DDR5 support, PCIe 5.0 support and so on – the Core i9-12900K is also the first 12th Gen chip to work with the Speed Optimizer tool in Intel’s Extreme Tuning Utility. This applies one-click overclocks to both the P-cores and E-cores, should you want to try overclocking but aren’t terribly comfortable going freestyle in the BIOS.

The Intel Core i9-12900K CPU installed in an LGA 1700 motherboard socket.

You’d be better off learning, though. The Speed Optimizer applied a 5GHz overclock on the P-cores, which was stable enough to avoid crashes. However, even with a 360mm AIO liquid cooler, temperatures rose to the point of throttling in Cinebench R20, while gaming performance remained unchanged.

An Asus ROG Ryujin II 360 cooler pump, with its built-in display showing a ROG logo.

Even on stock speeds, too, the Core i9-12900K really needs a decent liquid cooler to run at its best. I used an Asus ROG Ryujin II 360 for all the performance benchmarks above, and never detected any heat-induced throttling outside of overclock attempts, though the CPU can certainly get toasty when all 16 cores are putting the work in.

Asus ROG Ryujin II 360 Corsair H100i Elite LCD Cooler Master Hyper 212 Evo V2
Cinebench multicore average temps (°c ) 84 (P-cores), 73 (E-cores) 81 (P-cores), 72 (E-cores) 92 (P-cores), 75 (E-cores)
Cinebench multicore peak temp (°c ) 91 (P-core) 93 (P-core) 100 (P-core)

The entry-level Cooler Master air cooler, which capably chilled the Core i5-12900K, just couldn’t handle the Core i9-12900K when Cinebench was pushing all its cores at once; the E-cores were fine but sustained time in the 90-100°c is bad for performance and bad for the P-cores’ health. Asus and Corsair’s AIO liquid coolers were adequate, though still with brief jaunts into the 90°c-plus area.

The good news is that you shouldn’t see temperatures like this when playing games. Using the Ryujin II 360, repeated runs of the Shadow of the Tomb Raider benchmark saw P-core temperatures sticking within 40°c and 50°c, and Horizon Zero Dawn rarely pushed the chip past the low thirties. I’d still say get a liquid cooler to be safe, mind.

The rear side of an Intel Core i9-12900K CPU.

Admittedly, that may be another additional expense on top of a new motherboard, potentially new RAM and the Core i9-12900K itself; quite the shopping list to produce what could only be a handful of extra frames, depending on what you’re upgrading from. My advice? Stick with the Core i5-12600K. It’s hundreds of pounds/dollars less, is almost as good for games, and in desktop work can outmatch anything from Intel’s previous 11 generations. There’s a reason why it’s set to replace the Ryzen 5 5600X as our best CPU for gaming pick.

The Core i9-12900K is technically a contender for that too, at least in the sense that it will get you slightly more frames than anything else on the market. For people with cash to burn and a taste for the finer things, that alone is probably enough to make it a worthy purchase, especially considering Alder Lake will unlock high-speed PCIe 5.0 SSDs when they eventually appear. For everyone else, the i5 is the way to go.

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About the Author
James Archer avatar

James Archer

Hardware Editor

James had previously hung around beneath the RPS treehouse as a freelancer, before being told to drop the pine cones and climb up to become hardware editor. He has over a decade’s experience in testing/writing about tech and games, something you can probably tell from his hairline.